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<h2>Table of Contents</h2>
<ul>
<li><span class="stability_undefined"><a href="#buffer_buffer">Buffer</a></span><ul>
<li><span class="stability_undefined"><a href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe"><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code></a></span><ul>
<li><span class="stability_undefined"><a href="#buffer_the_zero_fill_buffers_command_line_option">The <code>--zero-fill-buffers</code> command line option</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?</a></span></li>
</ul>
</li>
<li><span class="stability_undefined"><a href="#buffer_buffers_and_character_encodings">Buffers and Character Encodings</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buffers_and_typedarray">Buffers and TypedArray</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buffers_and_iteration">Buffers and iteration</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_buffer">Class: Buffer</a></span><ul>
<li><span class="stability_0"><a href="#buffer_new_buffer_array">new Buffer(array)</a></span></li>
<li><span class="stability_0"><a href="#buffer_new_buffer_arraybuffer_byteoffset_length">new Buffer(arrayBuffer[, byteOffset [, length]])</a></span></li>
<li><span class="stability_0"><a href="#buffer_new_buffer_buffer">new Buffer(buffer)</a></span></li>
<li><span class="stability_0"><a href="#buffer_new_buffer_size">new Buffer(size)</a></span></li>
<li><span class="stability_0"><a href="#buffer_new_buffer_string_encoding">new Buffer(string[, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_alloc_size_fill_encoding">Class Method: Buffer.alloc(size[, fill[, encoding]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_allocunsafe_size">Class Method: Buffer.allocUnsafe(size)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_allocunsafeslow_size">Class Method: Buffer.allocUnsafeSlow(size)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_bytelength_string_encoding">Class Method: Buffer.byteLength(string[, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_compare_buf1_buf2">Class Method: Buffer.compare(buf1, buf2)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_concat_list_totallength">Class Method: Buffer.concat(list[, totalLength])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_from_array">Class Method: Buffer.from(array)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length">Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_from_buffer">Class Method: Buffer.from(buffer)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_from_string_encoding">Class Method: Buffer.from(string[, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_from_object_offsetorencoding_length">Class Method: Buffer.from(object[, offsetOrEncoding[, length]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_isbuffer_obj">Class Method: Buffer.isBuffer(obj)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_method_buffer_isencoding_encoding">Class Method: Buffer.isEncoding(encoding)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_class_property_buffer_poolsize">Class Property: Buffer.poolSize</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_index">buf[index]</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_buffer">buf.buffer</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend">buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_copy_target_targetstart_sourcestart_sourceend">buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_entries">buf.entries()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_equals_otherbuffer">buf.equals(otherBuffer)</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_fill_value_offset_end_encoding">buf.fill(value[, offset[, end]][, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_includes_value_byteoffset_encoding">buf.includes(value[, byteOffset][, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_indexof_value_byteoffset_encoding">buf.indexOf(value[, byteOffset][, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_keys">buf.keys()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_lastindexof_value_byteoffset_encoding">buf.lastIndexOf(value[, byteOffset][, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_length">buf.length</a></span></li>
<li><span class="stability_0"><a href="#buffer_buf_parent">buf.parent</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readdoublebe_offset_noassert">buf.readDoubleBE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readdoublele_offset_noassert">buf.readDoubleLE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readfloatbe_offset_noassert">buf.readFloatBE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readfloatle_offset_noassert">buf.readFloatLE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readint8_offset_noassert">buf.readInt8(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readint16be_offset_noassert">buf.readInt16BE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readint16le_offset_noassert">buf.readInt16LE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readint32be_offset_noassert">buf.readInt32BE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readint32le_offset_noassert">buf.readInt32LE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readintbe_offset_bytelength_noassert">buf.readIntBE(offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readintle_offset_bytelength_noassert">buf.readIntLE(offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuint8_offset_noassert">buf.readUInt8(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuint16be_offset_noassert">buf.readUInt16BE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuint16le_offset_noassert">buf.readUInt16LE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuint32be_offset_noassert">buf.readUInt32BE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuint32le_offset_noassert">buf.readUInt32LE(offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuintbe_offset_bytelength_noassert">buf.readUIntBE(offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_readuintle_offset_bytelength_noassert">buf.readUIntLE(offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_slice_start_end">buf.slice([start[, end]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_swap16">buf.swap16()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_swap32">buf.swap32()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_swap64">buf.swap64()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_tojson">buf.toJSON()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_tostring_encoding_start_end">buf.toString([encoding[, start[, end]]])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_values">buf.values()</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_write_string_offset_length_encoding">buf.write(string[, offset[, length]][, encoding])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writedoublebe_value_offset_noassert">buf.writeDoubleBE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writedoublele_value_offset_noassert">buf.writeDoubleLE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writefloatbe_value_offset_noassert">buf.writeFloatBE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writefloatle_value_offset_noassert">buf.writeFloatLE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeint8_value_offset_noassert">buf.writeInt8(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeint16be_value_offset_noassert">buf.writeInt16BE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeint16le_value_offset_noassert">buf.writeInt16LE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeint32be_value_offset_noassert">buf.writeInt32BE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeint32le_value_offset_noassert">buf.writeInt32LE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeintbe_value_offset_bytelength_noassert">buf.writeIntBE(value, offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeintle_value_offset_bytelength_noassert">buf.writeIntLE(value, offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuint8_value_offset_noassert">buf.writeUInt8(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuint16be_value_offset_noassert">buf.writeUInt16BE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuint16le_value_offset_noassert">buf.writeUInt16LE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuint32be_value_offset_noassert">buf.writeUInt32BE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuint32le_value_offset_noassert">buf.writeUInt32LE(value, offset[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuintbe_value_offset_bytelength_noassert">buf.writeUIntBE(value, offset, byteLength[, noAssert])</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buf_writeuintle_value_offset_bytelength_noassert">buf.writeUIntLE(value, offset, byteLength[, noAssert])</a></span></li>
</ul>
</li>
<li><span class="stability_undefined"><a href="#buffer_buffer_inspect_max_bytes">buffer.INSPECT_MAX_BYTES</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buffer_kmaxlength">buffer.kMaxLength</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buffer_transcode_source_fromenc_toenc">buffer.transcode(source, fromEnc, toEnc)</a></span></li>
<li><span class="stability_0"><a href="#buffer_class_slowbuffer">Class: SlowBuffer</a></span><ul>
<li><span class="stability_0"><a href="#buffer_new_slowbuffer_size">new SlowBuffer(size)</a></span></li>
</ul>
</li>
<li><span class="stability_undefined"><a href="#buffer_buffer_constants">Buffer Constants</a></span><ul>
<li><span class="stability_undefined"><a href="#buffer_buffer_constants_max_length">buffer.constants.MAX_LENGTH</a></span></li>
<li><span class="stability_undefined"><a href="#buffer_buffer_constants_max_string_length">buffer.constants.MAX_STRING_LENGTH</a></span></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<div id="apicontent">
<h1>Buffer<span><a class="mark" href="#buffer_buffer" id="buffer_buffer">#</a></span></h1>
<!--introduced_in=v0.1.90-->
<!--lint disable maximum-line-length-->
<div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p>Prior to the introduction of <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, the JavaScript language had no
mechanism for reading or manipulating streams of binary data. The <code>Buffer</code> class
was introduced as part of the Node.js API to make it possible to interact with
octet streams in the context of things like TCP streams and file system
operations.</p>
<p>With <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> now available, the <code>Buffer</code> class implements the
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> API in a manner that is more optimized and suitable for Node.js.</p>
<p>Instances of the <code>Buffer</code> class are similar to arrays of integers but
correspond to fixed-sized, raw memory allocations outside the V8 heap.
The size of the <code>Buffer</code> is established when it is created and cannot be
changed.</p>
<p>The <code>Buffer</code> class is within the global scope, making it unlikely that one
would need to ever use <code>require('buffer').Buffer</code>.</p>
<pre><code class="lang-js">// Creates a zero-filled Buffer of length 10.
const buf1 = Buffer.alloc(10);
// Creates a Buffer of length 10, filled with 0x1.
const buf2 = Buffer.alloc(10, 1);
// Creates an uninitialized buffer of length 10.
// This is faster than calling Buffer.alloc() but the returned
// Buffer instance might contain old data that needs to be
// overwritten using either fill() or write().
const buf3 = Buffer.allocUnsafe(10);
// Creates a Buffer containing [0x1, 0x2, 0x3].
const buf4 = Buffer.from([1, 2, 3]);
// Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74].
const buf5 = Buffer.from('tést');
// Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].
const buf6 = Buffer.from('tést', 'latin1');
</code></pre>
<h2><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code><span><a class="mark" href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe" id="buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe">#</a></span></h2>
<p>In versions of Node.js prior to 6.0.0, <code>Buffer</code> instances were created using the
<code>Buffer</code> constructor function, which allocates the returned <code>Buffer</code>
differently based on what arguments are provided:</p>
<ul>
<li>Passing a number as the first argument to <code>Buffer()</code> (e.g. <code>new Buffer(10)</code>)
allocates a new <code>Buffer</code> object of the specified size. Prior to Node.js 8.0.0,
the memory allocated for such <code>Buffer</code> instances is <em>not</em> initialized and
<em>can contain sensitive data</em>. Such <code>Buffer</code> instances <em>must</em> be subsequently
initialized by using either <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> or by writing to the
entire <code>Buffer</code>. While this behavior is <em>intentional</em> to improve performance,
development experience has demonstrated that a more explicit distinction is
required between creating a fast-but-uninitialized <code>Buffer</code> versus creating a
slower-but-safer <code>Buffer</code>. Starting in Node.js 8.0.0, <code>Buffer(num)</code> and
<code>new Buffer(num)</code> will return a <code>Buffer</code> with initialized memory.</li>
<li>Passing a string, array, or <code>Buffer</code> as the first argument copies the
passed object's data into the <code>Buffer</code>.</li>
<li>Passing an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> returns a <code>Buffer</code> that
shares allocated memory with the given array buffer.</li>
</ul>
<p>Because the behavior of <code>new Buffer()</code> is different depending on the type of the
first argument, security and reliability issues can be inadvertently introduced
into applications when argument validation or <code>Buffer</code> initialization is not
performed.</p>
<p>To make the creation of <code>Buffer</code> instances more reliable and less error-prone,
the various forms of the <code>new Buffer()</code> constructor have been <strong>deprecated</strong>
and replaced by separate <code>Buffer.from()</code>, <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a>, and
<a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> methods.</p>
<p><em>Developers should migrate all existing uses of the <code>new Buffer()</code> constructors
to one of these new APIs.</em></p>
<ul>
<li><a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the
provided octets.</li>
<li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset [, length]])</code></a>
returns a new <code>Buffer</code> that <em>shares the same allocated memory</em> as the given
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>.</li>
<li><a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the
contents of the given <code>Buffer</code>.</li>
<li><a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a> returns a new
<code>Buffer</code> that <em>contains a copy</em> of the provided string.</li>
<li><a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc(size[, fill[, encoding]])</code></a> returns a new
initialized <code>Buffer</code> of the specified size. This method is slower than
<a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> but guarantees that newly
created <code>Buffer</code> instances never contain old data that is potentially
sensitive.</li>
<li><a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> and
<a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow(size)</code></a> each return a
new uninitialized <code>Buffer</code> of the specified <code>size</code>. Because the <code>Buffer</code> is
uninitialized, the allocated segment of memory might contain old data that is
potentially sensitive.</li>
</ul>
<p><code>Buffer</code> instances returned by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> <em>may</em> be allocated off
a shared internal memory pool if <code>size</code> is less than or equal to half
<a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a>. Instances returned by <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a> <em>never</em>
use the shared internal memory pool.</p>
<h3>The <code>--zero-fill-buffers</code> command line option<span><a class="mark" href="#buffer_the_zero_fill_buffers_command_line_option" id="buffer_the_zero_fill_buffers_command_line_option">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><p>Node.js can be started using the <code>--zero-fill-buffers</code> command line option to
cause all newly allocated <code>Buffer</code> instances to be zero-filled upon creation by
default, including buffers returned by <code>new Buffer(size)</code>,
<a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>, <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, and <code>new
SlowBuffer(size)</code>. Use of this flag can have a significant negative impact on
performance. Use of the <code>--zero-fill-buffers</code> option is recommended only when
necessary to enforce that newly allocated <code>Buffer</code> instances cannot contain old
data that is potentially sensitive.</p>
<pre><code class="lang-txt">$ node --zero-fill-buffers
> Buffer.allocUnsafe(5);
<Buffer 00 00 00 00 00>
</code></pre>
<h3>What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?<span><a class="mark" href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe" id="buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">#</a></span></h3>
<p>When calling <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> and <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, the
segment of allocated memory is <em>uninitialized</em> (it is not zeroed-out). While
this design makes the allocation of memory quite fast, the allocated segment of
memory might contain old data that is potentially sensitive. Using a <code>Buffer</code>
created by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> without <em>completely</em> overwriting the memory
can allow this old data to be leaked when the <code>Buffer</code> memory is read.</p>
<p>While there are clear performance advantages to using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>,
extra care <em>must</em> be taken in order to avoid introducing security
vulnerabilities into an application.</p>
<h2>Buffers and Character Encodings<span><a class="mark" href="#buffer_buffers_and_character_encodings" id="buffer_buffers_and_character_encodings">#</a></span></h2>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v6.4.0</td>
<td><p>Introduced <code>latin1</code> as an alias for <code>binary</code>.</p>
</td></tr>
<tr><td>v5.0.0</td>
<td><p>Removed the deprecated <code>raw</code> and <code>raws</code> encodings.</p>
</td></tr>
</table>
</details>
</div><p>When string data is stored in or extracted out of a <code>Buffer</code> instance, a
character encoding may be specified.</p>
<pre><code class="lang-js">const buf = Buffer.from('hello world', 'ascii');
console.log(buf.toString('hex'));
// Prints: 68656c6c6f20776f726c64
console.log(buf.toString('base64'));
// Prints: aGVsbG8gd29ybGQ=
console.log(Buffer.from('fhqwhgads', 'ascii'));
// Prints: <Buffer 66 68 71 77 68 67 61 64 73>
console.log(Buffer.from('fhqwhgads', 'utf16le'));
// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>
</code></pre>
<p>The character encodings currently supported by Node.js include:</p>
<ul>
<li><p><code>'ascii'</code> - For 7-bit ASCII data only. This encoding is fast and will strip
the high bit if set.</p>
</li>
<li><p><code>'utf8'</code> - Multibyte encoded Unicode characters. Many web pages and other
document formats use UTF-8.</p>
</li>
<li><p><code>'utf16le'</code> - 2 or 4 bytes, little-endian encoded Unicode characters.
Surrogate pairs (U+10000 to U+10FFFF) are supported.</p>
</li>
<li><p><code>'ucs2'</code> - Alias of <code>'utf16le'</code>.</p>
</li>
<li><p><code>'base64'</code> - Base64 encoding. When creating a <code>Buffer</code> from a string,
this encoding will also correctly accept "URL and Filename Safe Alphabet" as
specified in <a href="https://tools.ietf.org/html/rfc4648#section-5">RFC4648, Section 5</a>.</p>
</li>
<li><p><code>'latin1'</code> - A way of encoding the <code>Buffer</code> into a one-byte encoded string
(as defined by the IANA in <a href="https://tools.ietf.org/html/rfc1345">RFC1345</a>,
page 63, to be the Latin-1 supplement block and C0/C1 control codes).</p>
</li>
<li><p><code>'binary'</code> - Alias for <code>'latin1'</code>.</p>
</li>
<li><p><code>'hex'</code> - Encode each byte as two hexadecimal characters.</p>
</li>
</ul>
<p>Modern Web browsers follow the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> which aliases
both <code>'latin1'</code> and <code>'ISO-8859-1'</code> to <code>'win-1252'</code>. This means that while doing
something like <code>http.get()</code>, if the returned charset is one of those listed in
the WHATWG specification it is possible that the server actually returned
win-1252-encoded data, and using <code>'latin1'</code> encoding may incorrectly decode the
characters.</p>
<h2>Buffers and TypedArray<span><a class="mark" href="#buffer_buffers_and_typedarray" id="buffer_buffers_and_typedarray">#</a></span></h2>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v3.0.0</td>
<td><p>The <code>Buffer</code>s class now inherits from <code>Uint8Array</code>.</p>
</td></tr>
</table>
</details>
</div><p><code>Buffer</code> instances are also <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> instances. However, there are subtle
incompatibilities with <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>. For example, while
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/slice"><code>ArrayBuffer#slice()</code></a> creates a copy of the slice, the implementation of
<a href="#buffer_buf_slice_start_end"><code>Buffer#slice()</code></a> creates a view over the existing <code>Buffer</code>
without copying, making <a href="#buffer_buf_slice_start_end"><code>Buffer#slice()</code></a> far more efficient.</p>
<p>It is also possible to create new <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instances from a <code>Buffer</code> with
the following caveats:</p>
<ol>
<li><p>The <code>Buffer</code> object's memory is copied to the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, not shared.</p>
</li>
<li><p>The <code>Buffer</code> object's memory is interpreted as an array of distinct
elements, and not as a byte array of the target type. That is,
<code>new Uint32Array(Buffer.from([1, 2, 3, 4]))</code> creates a 4-element <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a>
with elements <code>[1, 2, 3, 4]</code>, not a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> with a single element
<code>[0x1020304]</code> or <code>[0x4030201]</code>.</p>
</li>
</ol>
<p>It is possible to create a new <code>Buffer</code> that shares the same allocated memory as
a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance by using the TypeArray object's <code>.buffer</code> property.</p>
<pre><code class="lang-js">const arr = new Uint16Array(2);
arr[0] = 5000;
arr[1] = 4000;
// Copies the contents of `arr`
const buf1 = Buffer.from(arr);
// Shares memory with `arr`
const buf2 = Buffer.from(arr.buffer);
console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 a0 0f>
arr[1] = 6000;
console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 70 17>
</code></pre>
<p>Note that when creating a <code>Buffer</code> using a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>'s <code>.buffer</code>, it is
possible to use only a portion of the underlying <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> by passing in
<code>byteOffset</code> and <code>length</code> parameters.</p>
<pre><code class="lang-js">const arr = new Uint16Array(20);
const buf = Buffer.from(arr.buffer, 0, 16);
console.log(buf.length);
// Prints: 16
</code></pre>
<p>The <code>Buffer.from()</code> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from"><code>TypedArray.from()</code></a> have different signatures and
implementations. Specifically, the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> variants accept a second
argument that is a mapping function that is invoked on every element of the
typed array:</p>
<ul>
<li><code>TypedArray.from(source[, mapFn[, thisArg]])</code></li>
</ul>
<p>The <code>Buffer.from()</code> method, however, does not support the use of a mapping
function:</p>
<ul>
<li><a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a></li>
<li><a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a></li>
<li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset [, length]])</code></a></li>
<li><a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a></li>
</ul>
<h2>Buffers and iteration<span><a class="mark" href="#buffer_buffers_and_iteration" id="buffer_buffers_and_iteration">#</a></span></h2>
<p><code>Buffer</code> instances can be iterated over using <code>for..of</code> syntax:</p>
<pre><code class="lang-js">const buf = Buffer.from([1, 2, 3]);
// Prints:
// 1
// 2
// 3
for (const b of buf) {
console.log(b);
}
</code></pre>
<p>Additionally, the <a href="#buffer_buf_values"><code>buf.values()</code></a>, <a href="#buffer_buf_keys"><code>buf.keys()</code></a>, and
<a href="#buffer_buf_entries"><code>buf.entries()</code></a> methods can be used to create iterators.</p>
<h2>Class: Buffer<span><a class="mark" href="#buffer_class_buffer" id="buffer_class_buffer">#</a></span></h2>
<p>The <code>Buffer</code> class is a global type for dealing with binary data directly.
It can be constructed in a variety of ways.</p>
<h3>new Buffer(array)<span><a class="mark" href="#buffer_new_buffer_array" id="buffer_new_buffer_array">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.2.1</td>
<td><p>Calling this constructor no longer emits a deprecation warning.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>Calling this constructor emits a deprecation warning now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Deprecated since: v6.0.0</span></p>
</td></tr>
</table>
</details>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a> instead.</div><ul>
<li><code>array</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a> An array of bytes to copy from.</li>
</ul>
<p>Allocates a new <code>Buffer</code> using an <code>array</code> of octets.</p>
<pre><code class="lang-js">// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'
const buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
</code></pre>
<h3>new Buffer(arrayBuffer[, byteOffset [, length]])<span><a class="mark" href="#buffer_new_buffer_arraybuffer_byteoffset_length" id="buffer_new_buffer_arraybuffer_byteoffset_length">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.2.1</td>
<td><p>Calling this constructor no longer emits a deprecation warning.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>Calling this constructor emits a deprecation warning now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p>The <code>byteOffset</code> and <code>length</code> parameters are supported now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Deprecated since: v6.0.0</span></p>
</td></tr>
<tr><td>v3.0.0</td>
<td><p><span>Added in: v3.0.0</span></p>
</td></tr>
</table>
</details>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset [, length]])</code></a> instead.</div><ul>
<li><code>arrayBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> An <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>,
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> or the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</li>
<li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Index of first byte to expose. <strong>Default:</strong> <code>0</code></li>
<li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to expose.
<strong>Default:</strong> <code>arrayBuffer.length - byteOffset</code></li>
</ul>
<p>This creates a view of the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> without
copying the underlying memory. For example, when passed a reference to the
<code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance, the newly created <code>Buffer</code> will
share the same allocated memory as the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</p>
<p>The optional <code>byteOffset</code> and <code>length</code> arguments specify a memory range within
the <code>arrayBuffer</code> that will be shared by the <code>Buffer</code>.</p>
<pre><code class="lang-js">const arr = new Uint16Array(2);
arr[0] = 5000;
arr[1] = 4000;
// Shares memory with `arr`
const buf = new Buffer(arr.buffer);
console.log(buf);
// Prints: <Buffer 88 13 a0 0f>
// Changing the original Uint16Array changes the Buffer also
arr[1] = 6000;
console.log(buf);
// Prints: <Buffer 88 13 70 17>
</code></pre>
<h3>new Buffer(buffer)<span><a class="mark" href="#buffer_new_buffer_buffer" id="buffer_new_buffer_buffer">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.2.1</td>
<td><p>Calling this constructor no longer emits a deprecation warning.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>Calling this constructor emits a deprecation warning now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Deprecated since: v6.0.0</span></p>
</td></tr>
</table>
</details>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a> instead.</div><ul>
<li><code>buffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> An existing <code>Buffer</code> to copy data from.</li>
</ul>
<p>Copies the passed <code>buffer</code> data onto a new <code>Buffer</code> instance.</p>
<pre><code class="lang-js">const buf1 = new Buffer('buffer');
const buf2 = new Buffer(buf1);
buf1[0] = 0x61;
console.log(buf1.toString());
// Prints: auffer
console.log(buf2.toString());
// Prints: buffer
</code></pre>
<h3>new Buffer(size)<span><a class="mark" href="#buffer_new_buffer_size" id="buffer_new_buffer_size">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>new Buffer(size) will return zero-filled memory by default.</p>
</td></tr>
<tr><td>v7.2.1</td>
<td><p>Calling this constructor no longer emits a deprecation warning.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>Calling this constructor emits a deprecation warning now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Deprecated since: v6.0.0</span></p>
</td></tr>
</table>
</details>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a> instead (also see <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>).</div><ul>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li>
</ul>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If the <code>size</code> is larger than
<a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, a <a href="errors.html#errors_class_rangeerror"><code>RangeError</code></a> will be
thrown. A zero-length <code>Buffer</code> will be created if <code>size</code> is 0.</p>
<p>Prior to Node.js 8.0.0, the underlying memory for <code>Buffer</code> instances
created in this way is <em>not initialized</em>. The contents of a newly created
<code>Buffer</code> are unknown and <em>may contain sensitive data</em>. Use
<a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc(size)</code></a> instead to initialize a <code>Buffer</code>
with zeroes.</p>
<pre><code class="lang-js">const buf = new Buffer(10);
console.log(buf);
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>
</code></pre>
<h3>new Buffer(string[, encoding])<span><a class="mark" href="#buffer_new_buffer_string_encoding" id="buffer_new_buffer_string_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.2.1</td>
<td><p>Calling this constructor no longer emits a deprecation warning.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>Calling this constructor emits a deprecation warning now.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Deprecated since: v6.0.0</span></p>
</td></tr>
</table>
</details>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a> instead.</div><ul>
<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String to encode.</li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code></li>
</ul>
<p>Creates a new <code>Buffer</code> containing <code>string</code>. The <code>encoding</code> parameter identifies
the character encoding of <code>string</code>.</p>
<pre><code class="lang-js">const buf1 = new Buffer('this is a tést');
const buf2 = new Buffer('7468697320697320612074c3a97374', 'hex');
console.log(buf1.toString());
// Prints: this is a tést
console.log(buf2.toString());
// Prints: this is a tést
console.log(buf1.toString('ascii'));
// Prints: this is a tC)st
</code></pre>
<h3>Class Method: Buffer.alloc(size[, fill[, encoding]])<span><a class="mark" href="#buffer_class_method_buffer_alloc_size_fill_encoding" id="buffer_class_method_buffer_alloc_size_fill_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v9.2.1</td>
<td><p>Specifying an invalid string for <code>fill</code> now results in a zero-filled buffer.</p>
</td></tr>
<tr><td>v5.10.0</td>
<td><p><span>Added in: v5.10.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li>
<li><code>fill</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> A value to pre-fill the new <code>Buffer</code> with.
<strong>Default:</strong> <code>0</code></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>fill</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
</ul>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>fill</code> is <code>undefined</code>, the
<code>Buffer</code> will be <em>zero-filled</em>.</p>
<pre><code class="lang-js">const buf = Buffer.alloc(5);
console.log(buf);
// Prints: <Buffer 00 00 00 00 00>
</code></pre>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If the <code>size</code> is larger than
<a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, a <a href="errors.html#errors_class_rangeerror"><code>RangeError</code></a> will be
thrown. A zero-length <code>Buffer</code> will be created if <code>size</code> is 0.</p>
<p>If <code>fill</code> is specified, the allocated <code>Buffer</code> will be initialized by calling
<a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(fill)</code></a>.</p>
<pre><code class="lang-js">const buf = Buffer.alloc(5, 'a');
console.log(buf);
// Prints: <Buffer 61 61 61 61 61>
</code></pre>
<p>If both <code>fill</code> and <code>encoding</code> are specified, the allocated <code>Buffer</code> will be
initialized by calling <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(fill, encoding)</code></a>.</p>
<pre><code class="lang-js">const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');
console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
</code></pre>
<p>Calling <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a> can be significantly slower than the alternative
<a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> but ensures that the newly created <code>Buffer</code> instance
contents will <em>never contain sensitive data</em>.</p>
<p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p>
<h3>Class Method: Buffer.allocUnsafe(size)<span><a class="mark" href="#buffer_class_method_buffer_allocunsafe_size" id="buffer_class_method_buffer_allocunsafe_size">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.0.0</td>
<td><p>Passing a negative <code>size</code> will now throw an error.</p>
</td></tr>
<tr><td>v5.10.0</td>
<td><p><span>Added in: v5.10.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li>
</ul>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If the <code>size</code> is larger than
<a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, a <a href="errors.html#errors_class_rangeerror"><code>RangeError</code></a> will be
thrown. A zero-length <code>Buffer</code> will be created if <code>size</code> is 0.</p>
<p>The underlying memory for <code>Buffer</code> instances created in this way is <em>not
initialized</em>. The contents of the newly created <code>Buffer</code> are unknown and
<em>may contain sensitive data</em>. Use <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a> instead to initialize
<code>Buffer</code> instances with zeroes.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(10);
console.log(buf);
// Prints: (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>
buf.fill(0);
console.log(buf);
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>
</code></pre>
<p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p>
<p>Note that the <code>Buffer</code> module pre-allocates an internal <code>Buffer</code> instance of
size <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a> that is used as a pool for the fast allocation of new
<code>Buffer</code> instances created using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> and the deprecated
<code>new Buffer(size)</code> constructor only when <code>size</code> is less than or equal to
<code>Buffer.poolSize >> 1</code> (floor of <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a> divided by two).</p>
<p>Use of this pre-allocated internal memory pool is a key difference between
calling <code>Buffer.alloc(size, fill)</code> vs. <code>Buffer.allocUnsafe(size).fill(fill)</code>.
Specifically, <code>Buffer.alloc(size, fill)</code> will <em>never</em> use the internal <code>Buffer</code>
pool, while <code>Buffer.allocUnsafe(size).fill(fill)</code> <em>will</em> use the internal
<code>Buffer</code> pool if <code>size</code> is less than or equal to half <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a>. The
difference is subtle but can be important when an application requires the
additional performance that <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> provides.</p>
<h3>Class Method: Buffer.allocUnsafeSlow(size)<span><a class="mark" href="#buffer_class_method_buffer_allocunsafeslow_size" id="buffer_class_method_buffer_allocunsafeslow_size">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.12.0</span>
</div><ul>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li>
</ul>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If the <code>size</code> is larger than
<a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, a <a href="errors.html#errors_class_rangeerror"><code>RangeError</code></a> will be
thrown. A zero-length <code>Buffer</code> will be created if <code>size</code> is 0.</p>
<p>The underlying memory for <code>Buffer</code> instances created in this way is <em>not
initialized</em>. The contents of the newly created <code>Buffer</code> are unknown and
<em>may contain sensitive data</em>. Use <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> to initialize
such <code>Buffer</code> instances with zeroes.</p>
<p>When using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> to allocate new <code>Buffer</code> instances,
allocations under 4KB are sliced from a single pre-allocated <code>Buffer</code>. This
allows applications to avoid the garbage collection overhead of creating many
individually allocated <code>Buffer</code> instances. This approach improves both
performance and memory usage by eliminating the need to track and clean up as
many persistent objects.</p>
<p>However, in the case where a developer may need to retain a small chunk of
memory from a pool for an indeterminate amount of time, it may be appropriate
to create an un-pooled <code>Buffer</code> instance using <code>Buffer.allocUnsafeSlow()</code> and
then copying out the relevant bits.</p>
<pre><code class="lang-js">// Need to keep around a few small chunks of memory
const store = [];
socket.on('readable', () => {
const data = socket.read();
// Allocate for retained data
const sb = Buffer.allocUnsafeSlow(10);
// Copy the data into the new allocation
data.copy(sb, 0, 0, 10);
store.push(sb);
});
</code></pre>
<p><code>Buffer.allocUnsafeSlow()</code> should be used only as a last resort after a
developer has observed undue memory retention in their applications.</p>
<p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p>
<h3>Class Method: Buffer.byteLength(string[, encoding])<span><a class="mark" href="#buffer_class_method_buffer_bytelength_string_encoding" id="buffer_class_method_buffer_bytelength_string_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.0.0</td>
<td><p>Passing invalid input will now throw an error.</p>
</td></tr>
<tr><td>v5.10.0</td>
<td><p>The <code>string</code> parameter can now be any <code>TypedArray</code>, <code>DataView</code> or <code>ArrayBuffer</code>.</p>
</td></tr>
<tr><td>v0.1.90</td>
<td><p><span>Added in: v0.1.90</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> A
value to calculate the length of.</li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>string</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of bytes contained within <code>string</code>.</li>
</ul>
<p>Returns the actual byte length of a string. This is not the same as
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length"><code>String.prototype.length</code></a> since that returns the number of <em>characters</em> in
a string.</p>
<p>For <code>'base64'</code> and <code>'hex'</code>, this function assumes valid input. For strings that
contain non-Base64/Hex-encoded data (e.g. whitespace), the return value might be
greater than the length of a <code>Buffer</code> created from the string.</p>
<pre><code class="lang-js">const str = '\u00bd + \u00bc = \u00be';
console.log(`${str}: ${str.length} characters, ` +
`${Buffer.byteLength(str, 'utf8')} bytes`);
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes
</code></pre>
<p>When <code>string</code> is a <code>Buffer</code>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView"><code>DataView</code></a>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>/
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>, the actual byte length is returned.</p>
<h3>Class Method: Buffer.compare(buf1, buf2)<span><a class="mark" href="#buffer_class_method_buffer_compare_buf1_buf2" id="buffer_class_method_buffer_compare_buf1_buf2">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The arguments can now be <code>Uint8Array</code>s.</p>
</td></tr>
<tr><td>v0.11.13</td>
<td><p><span>Added in: v0.11.13</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>buf1</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li>
<li><code>buf2</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Compares <code>buf1</code> to <code>buf2</code> typically for the purpose of sorting arrays of
<code>Buffer</code> instances. This is equivalent to calling
<a href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend"><code>buf1.compare(buf2)</code></a>.</p>
<pre><code class="lang-js">const buf1 = Buffer.from('1234');
const buf2 = Buffer.from('0123');
const arr = [buf1, buf2];
console.log(arr.sort(Buffer.compare));
// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]
// (This result is equal to: [buf2, buf1])
</code></pre>
<h3>Class Method: Buffer.concat(list[, totalLength])<span><a class="mark" href="#buffer_class_method_buffer_concat_list_totallength" id="buffer_class_method_buffer_concat_list_totallength">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The elements of <code>list</code> can now be <code>Uint8Array</code>s.</p>
</td></tr>
<tr><td>v0.7.11</td>
<td><p><span>Added in: v0.7.11</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>list</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> List of <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> instances to concat.</li>
<li><code>totalLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Total length of the <code>Buffer</code> instances in <code>list</code>
when concatenated.</li>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li>
</ul>
<p>Returns a new <code>Buffer</code> which is the result of concatenating all the <code>Buffer</code>
instances in the <code>list</code> together.</p>
<p>If the list has no items, or if the <code>totalLength</code> is 0, then a new zero-length
<code>Buffer</code> is returned.</p>
<p>If <code>totalLength</code> is not provided, it is calculated from the <code>Buffer</code> instances
in <code>list</code>. This however causes an additional loop to be executed in order to
calculate the <code>totalLength</code>, so it is faster to provide the length explicitly if
it is already known.</p>
<p>If <code>totalLength</code> is provided, it is coerced to an unsigned integer. If the
combined length of the <code>Buffer</code>s in <code>list</code> exceeds <code>totalLength</code>, the result is
truncated to <code>totalLength</code>.</p>
<pre><code class="lang-js">// Create a single `Buffer` from a list of three `Buffer` instances.
const buf1 = Buffer.alloc(10);
const buf2 = Buffer.alloc(14);
const buf3 = Buffer.alloc(18);
const totalLength = buf1.length + buf2.length + buf3.length;
console.log(totalLength);
// Prints: 42
const bufA = Buffer.concat([buf1, buf2, buf3], totalLength);
console.log(bufA);
// Prints: <Buffer 00 00 00 00 ...>
console.log(bufA.length);
// Prints: 42
</code></pre>
<h3>Class Method: Buffer.from(array)<span><a class="mark" href="#buffer_class_method_buffer_from_array" id="buffer_class_method_buffer_from_array">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li><code>array</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a></li>
</ul>
<p>Allocates a new <code>Buffer</code> using an <code>array</code> of octets.</p>
<pre><code class="lang-js">// Creates a new Buffer containing UTF-8 bytes of the string 'buffer'
const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
</code></pre>
<p>A <code>TypeError</code> will be thrown if <code>array</code> is not an <code>Array</code>.</p>
<h3>Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])<span><a class="mark" href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length" id="buffer_class_method_buffer_from_arraybuffer_byteoffset_length">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li><code>arrayBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> An <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>,
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>, or the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</li>
<li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Index of first byte to expose. <strong>Default:</strong> <code>0</code></li>
<li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to expose.
<strong>Default:</strong> <code>arrayBuffer.length - byteOffset</code></li>
</ul>
<p>This creates a view of the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> without copying the underlying
memory. For example, when passed a reference to the <code>.buffer</code> property of a
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance, the newly created <code>Buffer</code> will share the same
allocated memory as the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</p>
<pre><code class="lang-js">const arr = new Uint16Array(2);
arr[0] = 5000;
arr[1] = 4000;
// Shares memory with `arr`
const buf = Buffer.from(arr.buffer);
console.log(buf);
// Prints: <Buffer 88 13 a0 0f>
// Changing the original Uint16Array changes the Buffer also
arr[1] = 6000;
console.log(buf);
// Prints: <Buffer 88 13 70 17>
</code></pre>
<p>The optional <code>byteOffset</code> and <code>length</code> arguments specify a memory range within
the <code>arrayBuffer</code> that will be shared by the <code>Buffer</code>.</p>
<pre><code class="lang-js">const ab = new ArrayBuffer(10);
const buf = Buffer.from(ab, 0, 2);
console.log(buf.length);
// Prints: 2
</code></pre>
<p>A <code>TypeError</code> will be thrown if <code>arrayBuffer</code> is not an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or a
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>.</p>
<h3>Class Method: Buffer.from(buffer)<span><a class="mark" href="#buffer_class_method_buffer_from_buffer" id="buffer_class_method_buffer_from_buffer">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li><code>buffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> An existing <code>Buffer</code> to copy data from.</li>
</ul>
<p>Copies the passed <code>buffer</code> data onto a new <code>Buffer</code> instance.</p>
<pre><code class="lang-js">const buf1 = Buffer.from('buffer');
const buf2 = Buffer.from(buf1);
buf1[0] = 0x61;
console.log(buf1.toString());
// Prints: auffer
console.log(buf2.toString());
// Prints: buffer
</code></pre>
<p>A <code>TypeError</code> will be thrown if <code>buffer</code> is not a <code>Buffer</code>.</p>
<h3>Class Method: Buffer.from(string[, encoding])<span><a class="mark" href="#buffer_class_method_buffer_from_string_encoding" id="buffer_class_method_buffer_from_string_encoding">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string to encode.</li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code></li>
</ul>
<p>Creates a new <code>Buffer</code> containing <code>string</code>. The <code>encoding</code> parameter identifies
the character encoding of <code>string</code>.</p>
<pre><code class="lang-js">const buf1 = Buffer.from('this is a tést');
const buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');
console.log(buf1.toString());
// Prints: this is a tést
console.log(buf2.toString());
// Prints: this is a tést
console.log(buf1.toString('ascii'));
// Prints: this is a tC)st
</code></pre>
<p>A <code>TypeError</code> will be thrown if <code>string</code> is not a string.</p>
<h3>Class Method: Buffer.from(object[, offsetOrEncoding[, length]])<span><a class="mark" href="#buffer_class_method_buffer_from_object_offsetorencoding_length" id="buffer_class_method_buffer_from_object_offsetorencoding_length">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v8.2.0</span>
</div><ul>
<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> An object supporting <code>Symbol.toPrimitive</code> or <code>valueOf()</code></li>
<li><code>offsetOrEncoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A byte-offset or encoding, depending on
the value returned either by <code>object.valueOf()</code> or
<code>object[Symbol.toPrimitive]()</code>.</li>
<li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A length, depending on the value returned either by
<code>object.valueOf()</code> or <code>object[Symbol.toPrimitive]()</code>.</li>
</ul>
<p>For objects whose <code>valueOf()</code> function returns a value not strictly equal to
<code>object</code>, returns <code>Buffer.from(object.valueOf(), offsetOrEncoding, length)</code>.</p>
<pre><code class="lang-js">const buf = Buffer.from(new String('this is a test'));
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
</code></pre>
<p>For objects that support <code>Symbol.toPrimitive</code>, returns
<code>Buffer.from(object[Symbol.toPrimitive](), offsetOrEncoding, length)</code>.</p>
<pre><code class="lang-js">class Foo {
[Symbol.toPrimitive]() {
return 'this is a test';
}
}
const buf = Buffer.from(new Foo(), 'utf8');
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
</code></pre>
<h3>Class Method: Buffer.isBuffer(obj)<span><a class="mark" href="#buffer_class_method_buffer_isbuffer_obj" id="buffer_class_method_buffer_isbuffer_obj">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.1.101</span>
</div><ul>
<li><code>obj</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if <code>obj</code> is a <code>Buffer</code>, <code>false</code> otherwise.</p>
<h3>Class Method: Buffer.isEncoding(encoding)<span><a class="mark" href="#buffer_class_method_buffer_isencoding_encoding" id="buffer_class_method_buffer_isencoding_encoding">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.9.1</span>
</div><ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A character encoding name to check.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if <code>encoding</code> contains a supported character encoding, or <code>false</code>
otherwise.</p>
<h3>Class Property: Buffer.poolSize<span><a class="mark" href="#buffer_class_property_buffer_poolsize" id="buffer_class_property_buffer_poolsize">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.3</span>
</div><ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>8192</code></li>
</ul>
<p>This is the number of bytes used to determine the size of pre-allocated, internal
<code>Buffer</code> instances used for pooling. This value may be modified.</p>
<h3>buf[index]<span><a class="mark" href="#buffer_buf_index" id="buffer_buf_index">#</a></span></h3>
<div class="api_metadata">
</div><p>The index operator <code>[index]</code> can be used to get and set the octet at position
<code>index</code> in <code>buf</code>. The values refer to individual bytes, so the legal value
range is between <code>0x00</code> and <code>0xFF</code> (hex) or <code>0</code> and <code>255</code> (decimal).</p>
<p>This operator is inherited from <code>Uint8Array</code>, so its behavior on out-of-bounds
access is the same as <code>UInt8Array</code> - that is, getting returns <code>undefined</code> and
setting does nothing.</p>
<pre><code class="lang-js">// Copy an ASCII string into a `Buffer` one byte at a time.
const str = 'Node.js';
const buf = Buffer.allocUnsafe(str.length);
for (let i = 0; i < str.length; i++) {
buf[i] = str.charCodeAt(i);
}
console.log(buf.toString('ascii'));
// Prints: Node.js
</code></pre>
<h3>buf.buffer<span><a class="mark" href="#buffer_buf_buffer" id="buffer_buf_buffer">#</a></span></h3>
<p>The <code>buffer</code> property references the underlying <code>ArrayBuffer</code> object based on
which this Buffer object is created.</p>
<pre><code class="lang-js">const arrayBuffer = new ArrayBuffer(16);
const buffer = Buffer.from(arrayBuffer);
console.log(buffer.buffer === arrayBuffer);
// Prints: true
</code></pre>
<h3>buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])<span><a class="mark" href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend" id="buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The <code>target</code> parameter can now be a <code>Uint8Array</code>.</p>
</td></tr>
<tr><td>v5.11.0</td>
<td><p>Additional parameters for specifying offsets are supported now.</p>
</td></tr>
<tr><td>v0.11.13</td>
<td><p><span>Added in: v0.11.13</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>target</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> to compare to.</li>
<li><code>targetStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>target</code> at which to begin
comparison. <strong>Default:</strong> <code>0</code></li>
<li><code>targetEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset with <code>target</code> at which to end comparison
(not inclusive). <strong>Default:</strong> <code>target.length</code></li>
<li><code>sourceStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to begin comparison.
<strong>Default:</strong> <code>0</code></li>
<li><code>sourceEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to end comparison
(not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Compares <code>buf</code> with <code>target</code> and returns a number indicating whether <code>buf</code>
comes before, after, or is the same as <code>target</code> in sort order.
Comparison is based on the actual sequence of bytes in each <code>Buffer</code>.</p>
<ul>
<li><code>0</code> is returned if <code>target</code> is the same as <code>buf</code></li>
<li><code>1</code> is returned if <code>target</code> should come <em>before</em> <code>buf</code> when sorted.</li>
<li><code>-1</code> is returned if <code>target</code> should come <em>after</em> <code>buf</code> when sorted.</li>
</ul>
<pre><code class="lang-js">const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('BCD');
const buf3 = Buffer.from('ABCD');
console.log(buf1.compare(buf1));
// Prints: 0
console.log(buf1.compare(buf2));
// Prints: -1
console.log(buf1.compare(buf3));
// Prints: -1
console.log(buf2.compare(buf1));
// Prints: 1
console.log(buf2.compare(buf3));
// Prints: 1
console.log([buf1, buf2, buf3].sort(Buffer.compare));
// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]
// (This result is equal to: [buf1, buf3, buf2])
</code></pre>
<p>The optional <code>targetStart</code>, <code>targetEnd</code>, <code>sourceStart</code>, and <code>sourceEnd</code>
arguments can be used to limit the comparison to specific ranges within <code>target</code>
and <code>buf</code> respectively.</p>
<pre><code class="lang-js">const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);
console.log(buf1.compare(buf2, 5, 9, 0, 4));
// Prints: 0
console.log(buf1.compare(buf2, 0, 6, 4));
// Prints: -1
console.log(buf1.compare(buf2, 5, 6, 5));
// Prints: 1
</code></pre>
<p>A <code>RangeError</code> will be thrown if: <code>targetStart < 0</code>, <code>sourceStart < 0</code>,
<code>targetEnd > target.byteLength</code> or <code>sourceEnd > source.byteLength</code>.</p>
<h3>buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])<span><a class="mark" href="#buffer_buf_copy_target_targetstart_sourcestart_sourceend" id="buffer_buf_copy_target_targetstart_sourcestart_sourceend">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div><ul>
<li><code>target</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> to copy into.</li>
<li><code>targetStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>target</code> at which to begin
copying to. <strong>Default:</strong> <code>0</code></li>
<li><code>sourceStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to begin copying from.
<strong>Default:</strong> <code>0</code></li>
<li><code>sourceEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to stop copying (not
inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of bytes copied.</li>
</ul>
<p>Copies data from a region of <code>buf</code> to a region in <code>target</code> even if the <code>target</code>
memory region overlaps with <code>buf</code>.</p>
<pre><code class="lang-js">// Create two `Buffer` instances.
const buf1 = Buffer.allocUnsafe(26);
const buf2 = Buffer.allocUnsafe(26).fill('!');
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'
buf1[i] = i + 97;
}
// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`
buf1.copy(buf2, 8, 16, 20);
console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!
</code></pre>
<pre><code class="lang-js">// Create a `Buffer` and copy data from one region to an overlapping region
// within the same `Buffer`.
const buf = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'
buf[i] = i + 97;
}
buf.copy(buf, 0, 4, 10);
console.log(buf.toString());
// Prints: efghijghijklmnopqrstuvwxyz
</code></pre>
<h3>buf.entries()<span><a class="mark" href="#buffer_buf_entries" id="buffer_buf_entries">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v1.1.0</span>
</div><ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li>
</ul>
<p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> of <code>[index, byte]</code> pairs from the contents of
<code>buf</code>.</p>
<pre><code class="lang-js">// Log the entire contents of a `Buffer`.
const buf = Buffer.from('buffer');
for (const pair of buf.entries()) {
console.log(pair);
}
// Prints:
// [0, 98]
// [1, 117]
// [2, 102]
// [3, 102]
// [4, 101]
// [5, 114]
</code></pre>
<h3>buf.equals(otherBuffer)<span><a class="mark" href="#buffer_buf_equals_otherbuffer" id="buffer_buf_equals_otherbuffer">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The arguments can now be <code>Uint8Array</code>s.</p>
</td></tr>
<tr><td>v0.11.13</td>
<td><p><span>Added in: v0.11.13</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>otherBuffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> to compare to.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if both <code>buf</code> and <code>otherBuffer</code> have exactly the same bytes,
<code>false</code> otherwise.</p>
<pre><code class="lang-js">const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('414243', 'hex');
const buf3 = Buffer.from('ABCD');
console.log(buf1.equals(buf2));
// Prints: true
console.log(buf1.equals(buf3));
// Prints: false
</code></pre>
<h3>buf.fill(value[, offset[, end]][, encoding])<span><a class="mark" href="#buffer_buf_fill_value_offset_end_encoding" id="buffer_buf_fill_value_offset_end_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v5.7.0</td>
<td><p>The <code>encoding</code> parameter is supported now.</p>
</td></tr>
<tr><td>v0.5.0</td>
<td><p><span>Added in: v0.5.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The value to fill <code>buf</code> with.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to fill <code>buf</code>. <strong>Default:</strong> <code>0</code></li>
<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to stop filling <code>buf</code> (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li>
</ul>
<p>Fills <code>buf</code> with the specified <code>value</code>. If the <code>offset</code> and <code>end</code> are not given,
the entire <code>buf</code> will be filled. This is meant to be a small simplification to
allow the creation and filling of a <code>Buffer</code> to be done on a single line.</p>
<pre><code class="lang-js">// Fill a `Buffer` with the ASCII character 'h'.
const b = Buffer.allocUnsafe(50).fill('h');
console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
</code></pre>
<p><code>value</code> is coerced to a <code>uint32</code> value if it is not a String or Integer.</p>
<p>If the final write of a <code>fill()</code> operation falls on a multi-byte character,
then only the first bytes of that character that fit into <code>buf</code> are written.</p>
<pre><code class="lang-js">// Fill a `Buffer` with a two-byte character.
console.log(Buffer.allocUnsafe(3).fill('\u0222'));
// Prints: <Buffer c8 a2 c8>
</code></pre>
<p>If <code>value</code> contains invalid characters, it is truncated.</p>
<p>If no valid fill data remains, then the buffer is either zero-filled or no
filling is performed, depending on the input type. That behavior is dictated by
compatibility reasons and was changed to throwing an exception in Node.js v10,
so it's not recommended to rely on that.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(5);
console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.
</code></pre>
<h3>buf.includes(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_includes_value_byteoffset_encoding" id="buffer_buf_includes_value_byteoffset_encoding">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.3.0</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li>
<li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>. <strong>Default:</strong> <code>0</code></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if <code>value</code> was found in <code>buf</code>, <code>false</code> otherwise.</li>
</ul>
<p>Equivalent to <a href="#buffer_buf_indexof_value_byteoffset_encoding"><code>buf.indexOf() !== -1</code></a>.</p>
<pre><code class="lang-js">const buf = Buffer.from('this is a buffer');
console.log(buf.includes('this'));
// Prints: true
console.log(buf.includes('is'));
// Prints: true
console.log(buf.includes(Buffer.from('a buffer')));
// Prints: true
console.log(buf.includes(97));
// Prints: true (97 is the decimal ASCII value for 'a')
console.log(buf.includes(Buffer.from('a buffer example')));
// Prints: false
console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));
// Prints: true
console.log(buf.includes('this', 4));
// Prints: false
</code></pre>
<h3>buf.indexOf(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_indexof_value_byteoffset_encoding" id="buffer_buf_indexof_value_byteoffset_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The <code>value</code> can now be a <code>Uint8Array</code>.</p>
</td></tr>
<tr><td>v5.7.0, v4.4.0</td>
<td><p>When <code>encoding</code> is being passed, the <code>byteOffset</code> parameter is no longer required.</p>
</td></tr>
<tr><td>v1.5.0</td>
<td><p><span>Added in: v1.5.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li>
<li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>. <strong>Default:</strong> <code>0</code></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The index of the first occurrence of <code>value</code> in <code>buf</code> or <code>-1</code>
if <code>buf</code> does not contain <code>value</code>.</li>
</ul>
<p>If <code>value</code> is:</p>
<ul>
<li>a string, <code>value</code> is interpreted according to the character encoding in
<code>encoding</code>.</li>
<li>a <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a>, <code>value</code> will be used in its entirety.
To compare a partial <code>Buffer</code>, use <a href="#buffer_buf_slice_start_end"><code>buf.slice()</code></a>.</li>
<li>a number, <code>value</code> will be interpreted as an unsigned 8-bit integer
value between <code>0</code> and <code>255</code>.</li>
</ul>
<pre><code class="lang-js">const buf = Buffer.from('this is a buffer');
console.log(buf.indexOf('this'));
// Prints: 0
console.log(buf.indexOf('is'));
// Prints: 2
console.log(buf.indexOf(Buffer.from('a buffer')));
// Prints: 8
console.log(buf.indexOf(97));
// Prints: 8 (97 is the decimal ASCII value for 'a')
console.log(buf.indexOf(Buffer.from('a buffer example')));
// Prints: -1
console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));
// Prints: 8
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le'));
// Prints: 4
console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le'));
// Prints: 6
</code></pre>
<p>If <code>value</code> is not a string, number, or <code>Buffer</code>, this method will throw a
<code>TypeError</code>. If <code>value</code> is a number, it will be coerced to a valid byte value,
an integer between 0 and 255.</p>
<p>If <code>byteOffset</code> is not a number, it will be coerced to a number. Any arguments
that coerce to <code>NaN</code> or 0, like <code>{}</code>, <code>[]</code>, <code>null</code> or <code>undefined</code>, will search
the whole buffer. This behavior matches <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf"><code>String#indexOf()</code></a>.</p>
<pre><code class="lang-js">const b = Buffer.from('abcdef');
// Passing a value that's a number, but not a valid byte
// Prints: 2, equivalent to searching for 99 or 'c'
console.log(b.indexOf(99.9));
console.log(b.indexOf(256 + 99));
// Passing a byteOffset that coerces to NaN or 0
// Prints: 1, searching the whole buffer
console.log(b.indexOf('b', undefined));
console.log(b.indexOf('b', {}));
console.log(b.indexOf('b', null));
console.log(b.indexOf('b', []));
</code></pre>
<p>If <code>value</code> is an empty string or empty <code>Buffer</code> and <code>byteOffset</code> is less
than <code>buf.length</code>, <code>byteOffset</code> will be returned. If <code>value</code> is empty and
<code>byteOffset</code> is at least <code>buf.length</code>, <code>buf.length</code> will be returned.</p>
<h3>buf.keys()<span><a class="mark" href="#buffer_buf_keys" id="buffer_buf_keys">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v1.1.0</span>
</div><ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li>
</ul>
<p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> of <code>buf</code> keys (indices).</p>
<pre><code class="lang-js">const buf = Buffer.from('buffer');
for (const key of buf.keys()) {
console.log(key);
}
// Prints:
// 0
// 1
// 2
// 3
// 4
// 5
</code></pre>
<h3>buf.lastIndexOf(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_lastindexof_value_byteoffset_encoding" id="buffer_buf_lastindexof_value_byteoffset_encoding">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The <code>value</code> can now be a <code>Uint8Array</code>.</p>
</td></tr>
<tr><td>v6.0.0</td>
<td><p><span>Added in: v6.0.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li>
<li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>.
<strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a><code>- 1</code></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is its encoding.
<strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The index of the last occurrence of <code>value</code> in <code>buf</code> or <code>-1</code>
if <code>buf</code> does not contain <code>value</code>.</li>
</ul>
<p>Identical to <a href="#buffer_buf_indexof_value_byteoffset_encoding"><code>buf.indexOf()</code></a>, except <code>buf</code> is searched from back to front
instead of front to back.</p>
<pre><code class="lang-js">const buf = Buffer.from('this buffer is a buffer');
console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4
</code></pre>
<p>If <code>value</code> is not a string, number, or <code>Buffer</code>, this method will throw a
<code>TypeError</code>. If <code>value</code> is a number, it will be coerced to a valid byte value,
an integer between 0 and 255.</p>
<p>If <code>byteOffset</code> is not a number, it will be coerced to a number. Any arguments
that coerce to <code>NaN</code>, like <code>{}</code> or <code>undefined</code>, will search the whole buffer.
This behavior matches <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf"><code>String#lastIndexOf()</code></a>.</p>
<pre><code class="lang-js">const b = Buffer.from('abcdef');
// Passing a value that's a number, but not a valid byte
// Prints: 2, equivalent to searching for 99 or 'c'
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));
// Passing a byteOffset that coerces to NaN
// Prints: 1, searching the whole buffer
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));
// Passing a byteOffset that coerces to 0
// Prints: -1, equivalent to passing 0
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));
</code></pre>
<p>If <code>value</code> is an empty string or empty <code>Buffer</code>, <code>byteOffset</code> will be returned.</p>
<h3>buf.length<span><a class="mark" href="#buffer_buf_length" id="buffer_buf_length">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div><ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns the amount of memory allocated for <code>buf</code> in bytes. Note that this
does not necessarily reflect the amount of "usable" data within <code>buf</code>.</p>
<pre><code class="lang-js">// Create a `Buffer` and write a shorter ASCII string to it.
const buf = Buffer.alloc(1234);
console.log(buf.length);
// Prints: 1234
buf.write('some string', 0, 'ascii');
console.log(buf.length);
// Prints: 1234
</code></pre>
<p>While the <code>length</code> property is not immutable, changing the value of <code>length</code>
can result in undefined and inconsistent behavior. Applications that wish to
modify the length of a <code>Buffer</code> should therefore treat <code>length</code> as read-only and
use <a href="#buffer_buf_slice_start_end"><code>buf.slice()</code></a> to create a new <code>Buffer</code>.</p>
<pre><code class="lang-js">let buf = Buffer.allocUnsafe(10);
buf.write('abcdefghj', 0, 'ascii');
console.log(buf.length);
// Prints: 10
buf = buf.slice(0, 5);
console.log(buf.length);
// Prints: 5
</code></pre>
<h3>buf.parent<span><a class="mark" href="#buffer_buf_parent" id="buffer_buf_parent">#</a></span></h3>
<div class="api_metadata">
<span>Deprecated since: v8.0.0</span>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_buf_buffer"><code>buf.buffer</code></a> instead.</div><p>The <code>buf.parent</code> property is a deprecated alias for <code>buf.buffer</code>.</p>
<h3>buf.readDoubleBE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readdoublebe_offset_noassert" id="buffer_buf_readdoublebe_offset_noassert">#</a></span></h3>
<h3>buf.readDoubleLE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readdoublele_offset_noassert" id="buffer_buf_readdoublele_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 8</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>Reads a 64-bit double from <code>buf</code> at the specified <code>offset</code> with specified
endian format (<code>readDoubleBE()</code> returns big endian, <code>readDoubleLE()</code> returns
little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readDoubleBE());
// Prints: 8.20788039913184e-304
console.log(buf.readDoubleLE());
// Prints: 5.447603722011605e-270
console.log(buf.readDoubleLE(1));
// Throws an exception: RangeError: Index out of range
console.log(buf.readDoubleLE(1, true));
// Warning: reads passed end of buffer!
// This will result in a segmentation fault! Don't do this!
</code></pre>
<h3>buf.readFloatBE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readfloatbe_offset_noassert" id="buffer_buf_readfloatbe_offset_noassert">#</a></span></h3>
<h3>buf.readFloatLE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readfloatle_offset_noassert" id="buffer_buf_readfloatle_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>Reads a 32-bit float from <code>buf</code> at the specified <code>offset</code> with specified
endian format (<code>readFloatBE()</code> returns big endian, <code>readFloatLE()</code> returns
little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([1, 2, 3, 4]);
console.log(buf.readFloatBE());
// Prints: 2.387939260590663e-38
console.log(buf.readFloatLE());
// Prints: 1.539989614439558e-36
console.log(buf.readFloatLE(1));
// Throws an exception: RangeError: Index out of range
console.log(buf.readFloatLE(1, true));
// Warning: reads passed end of buffer!
// This will result in a segmentation fault! Don't do this!
</code></pre>
<h3>buf.readInt8(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readint8_offset_noassert" id="buffer_buf_readint8_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 1</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads a signed 8-bit integer from <code>buf</code> at the specified <code>offset</code>.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p>
<pre><code class="lang-js">const buf = Buffer.from([-1, 5]);
console.log(buf.readInt8(0));
// Prints: -1
console.log(buf.readInt8(1));
// Prints: 5
console.log(buf.readInt8(2));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readInt16BE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readint16be_offset_noassert" id="buffer_buf_readint16be_offset_noassert">#</a></span></h3>
<h3>buf.readInt16LE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readint16le_offset_noassert" id="buffer_buf_readint16le_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 2</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads a signed 16-bit integer from <code>buf</code> at the specified <code>offset</code> with
the specified endian format (<code>readInt16BE()</code> returns big endian,
<code>readInt16LE()</code> returns little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p>
<pre><code class="lang-js">const buf = Buffer.from([0, 5]);
console.log(buf.readInt16BE());
// Prints: 5
console.log(buf.readInt16LE());
// Prints: 1280
console.log(buf.readInt16LE(1));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readInt32BE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readint32be_offset_noassert" id="buffer_buf_readint32be_offset_noassert">#</a></span></h3>
<h3>buf.readInt32LE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readint32le_offset_noassert" id="buffer_buf_readint32le_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads a signed 32-bit integer from <code>buf</code> at the specified <code>offset</code> with
the specified endian format (<code>readInt32BE()</code> returns big endian,
<code>readInt32LE()</code> returns little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p>
<pre><code class="lang-js">const buf = Buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32BE());
// Prints: 5
console.log(buf.readInt32LE());
// Prints: 83886080
console.log(buf.readInt32LE(1));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readIntBE(offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_readintbe_offset_bytelength_noassert" id="buffer_buf_readintbe_offset_bytelength_noassert">#</a></span></h3>
<h3>buf.readIntLE(offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_readintle_offset_bytelength_noassert" id="buffer_buf_readintle_offset_bytelength_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - byteLength</code>.</li>
<li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to read. Must satisfy: <code>0 < byteLength <= 6</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> and <code>byteLength</code> validation? <strong>Default:</strong> <code>false</code>.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads <code>byteLength</code> number of bytes from <code>buf</code> at the specified <code>offset</code>
and interprets the result as a two's complement signed value. Supports up to 48
bits of accuracy.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readIntLE(0, 6).toString(16));
// Prints: -546f87a9cbee
console.log(buf.readIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readIntBE(1, 6).toString(16));
// Throws: RangeError [ERR_INDEX_OUT_OF_RANGE]: Index out of range
</code></pre>
<h3>buf.readUInt8(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readuint8_offset_noassert" id="buffer_buf_readuint8_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 1</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads an unsigned 8-bit integer from <code>buf</code> at the specified <code>offset</code>.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([1, -2]);
console.log(buf.readUInt8(0));
// Prints: 1
console.log(buf.readUInt8(1));
// Prints: 254
console.log(buf.readUInt8(2));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readUInt16BE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readuint16be_offset_noassert" id="buffer_buf_readuint16be_offset_noassert">#</a></span></h3>
<h3>buf.readUInt16LE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readuint16le_offset_noassert" id="buffer_buf_readuint16le_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 2</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads an unsigned 16-bit integer from <code>buf</code> at the specified <code>offset</code> with
specified endian format (<code>readUInt16BE()</code> returns big endian, <code>readUInt16LE()</code>
returns little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([0x12, 0x34, 0x56]);
console.log(buf.readUInt16BE(0).toString(16));
// Prints: 1234
console.log(buf.readUInt16LE(0).toString(16));
// Prints: 3412
console.log(buf.readUInt16BE(1).toString(16));
// Prints: 3456
console.log(buf.readUInt16LE(1).toString(16));
// Prints: 5634
console.log(buf.readUInt16LE(2).toString(16));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readUInt32BE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readuint32be_offset_noassert" id="buffer_buf_readuint32be_offset_noassert">#</a></span></h3>
<h3>buf.readUInt32LE(offset[, noAssert])<span><a class="mark" href="#buffer_buf_readuint32le_offset_noassert" id="buffer_buf_readuint32le_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads an unsigned 32-bit integer from <code>buf</code> at the specified <code>offset</code> with
specified endian format (<code>readUInt32BE()</code> returns big endian,
<code>readUInt32LE()</code> returns little endian).</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678
console.log(buf.readUInt32LE(0).toString(16));
// Prints: 78563412
console.log(buf.readUInt32LE(1).toString(16));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.readUIntBE(offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_readuintbe_offset_bytelength_noassert" id="buffer_buf_readuintbe_offset_bytelength_noassert">#</a></span></h3>
<h3>buf.readUIntLE(offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_readuintle_offset_bytelength_noassert" id="buffer_buf_readuintle_offset_bytelength_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy: <code>0 <= offset <= buf.length - byteLength</code>.</li>
<li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to read. Must satisfy: <code>0 < byteLength <= 6</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>offset</code> and <code>byteLength</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Reads <code>byteLength</code> number of bytes from <code>buf</code> at the specified <code>offset</code>
and interprets the result as an unsigned integer. Supports up to 48
bits of accuracy.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows <code>offset</code> to be beyond the end of <code>buf</code>, but
the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readUIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readUIntLE(0, 6).toString(16));
// Prints: ab9078563412
console.log(buf.readUIntBE(1, 6).toString(16));
// Throws an exception: RangeError: Index out of range
</code></pre>
<h3>buf.slice([start[, end]])<span><a class="mark" href="#buffer_buf_slice_start_end" id="buffer_buf_slice_start_end">#</a></span></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v7.1.0, v6.9.2</td>
<td><p>Coercing the offsets to integers now handles values outside the 32-bit integer range properly.</p>
</td></tr>
<tr><td>v7.0.0</td>
<td><p>All offsets are now coerced to integers before doing any calculations with them.</p>
</td></tr>
<tr><td>v0.3.0</td>
<td><p><span>Added in: v0.3.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where the new <code>Buffer</code> will start. <strong>Default:</strong> <code>0</code></li>
<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where the new <code>Buffer</code> will end (not inclusive).
<strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a></li>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li>
</ul>
<p>Returns a new <code>Buffer</code> that references the same memory as the original, but
offset and cropped by the <code>start</code> and <code>end</code> indices.</p>
<p>Specifying <code>end</code> greater than <a href="#buffer_buf_length"><code>buf.length</code></a> will return the same result as
that of <code>end</code> equal to <a href="#buffer_buf_length"><code>buf.length</code></a>.</p>
<p>Modifying the new <code>Buffer</code> slice will modify the memory in the original <code>Buffer</code>
because the allocated memory of the two objects overlap.</p>
<pre><code class="lang-js">// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.
const buf1 = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'
buf1[i] = i + 97;
}
const buf2 = buf1.slice(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc
buf1[0] = 33;
console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: !bc
</code></pre>
<p>Specifying negative indexes causes the slice to be generated relative to the
end of <code>buf</code> rather than the beginning.</p>
<pre><code class="lang-js">const buf = Buffer.from('buffer');
console.log(buf.slice(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.slice(0, 5))
console.log(buf.slice(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.slice(0, 4))
console.log(buf.slice(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.slice(1, 4))
</code></pre>
<h3>buf.swap16()<span><a class="mark" href="#buffer_buf_swap16" id="buffer_buf_swap16">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li>
</ul>
<p>Interprets <code>buf</code> as an array of unsigned 16-bit integers and swaps the byte-order
<em>in-place</em>. Throws a <code>RangeError</code> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 2.</p>
<pre><code class="lang-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap16();
console.log(buf1);
// Prints: <Buffer 02 01 04 03 06 05 08 07>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap16();
// Throws an exception: RangeError: Buffer size must be a multiple of 16-bits
</code></pre>
<h3>buf.swap32()<span><a class="mark" href="#buffer_buf_swap32" id="buffer_buf_swap32">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v5.10.0</span>
</div><ul>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li>
</ul>
<p>Interprets <code>buf</code> as an array of unsigned 32-bit integers and swaps the byte-order
<em>in-place</em>. Throws a <code>RangeError</code> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 4.</p>
<pre><code class="lang-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap32();
console.log(buf1);
// Prints: <Buffer 04 03 02 01 08 07 06 05>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap32();
// Throws an exception: RangeError: Buffer size must be a multiple of 32-bits
</code></pre>
<h3>buf.swap64()<span><a class="mark" href="#buffer_buf_swap64" id="buffer_buf_swap64">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v6.3.0</span>
</div><ul>
<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li>
</ul>
<p>Interprets <code>buf</code> as an array of 64-bit numbers and swaps the byte-order <em>in-place</em>.
Throws a <code>RangeError</code> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 8.</p>
<pre><code class="lang-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap64();
console.log(buf1);
// Prints: <Buffer 08 07 06 05 04 03 02 01>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap64();
// Throws an exception: RangeError: Buffer size must be a multiple of 64-bits
</code></pre>
<p>Note that JavaScript cannot encode 64-bit integers. This method is intended
for working with 64-bit floats.</p>
<h3>buf.toJSON()<span><a class="mark" href="#buffer_buf_tojson" id="buffer_buf_tojson">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.9.2</span>
</div><ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
</ul>
<p>Returns a JSON representation of <code>buf</code>. <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify"><code>JSON.stringify()</code></a> implicitly calls
this function when stringifying a <code>Buffer</code> instance.</p>
<pre><code class="lang-js">const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
const json = JSON.stringify(buf);
console.log(json);
// Prints: {"type":"Buffer","data":[1,2,3,4,5]}
const copy = JSON.parse(json, (key, value) => {
return value && value.type === 'Buffer' ?
Buffer.from(value.data) :
value;
});
console.log(copy);
// Prints: <Buffer 01 02 03 04 05>
</code></pre>
<h3>buf.toString([encoding[, start[, end]]])<span><a class="mark" href="#buffer_buf_tostring_encoding_start_end" id="buffer_buf_tostring_encoding_start_end">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div><ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The character encoding to decode to. <strong>Default:</strong> <code>'utf8'</code></li>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The byte offset to start decoding at. <strong>Default:</strong> <code>0</code></li>
<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The byte offset to stop decoding at (not inclusive).
<strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Decodes <code>buf</code> to a string according to the specified character encoding in
<code>encoding</code>. <code>start</code> and <code>end</code> may be passed to decode only a subset of <code>buf</code>.</p>
<p>The maximum length of a string instance (in UTF-16 code units) is available
as <a href="#buffer_buffer_constants_max_string_length"><code>buffer.constants.MAX_STRING_LENGTH</code></a>.</p>
<pre><code class="lang-js">const buf1 = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'
buf1[i] = i + 97;
}
console.log(buf1.toString('ascii'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('ascii', 0, 5));
// Prints: abcde
const buf2 = Buffer.from('tést');
console.log(buf2.toString('hex'));
// Prints: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// Prints: té
console.log(buf2.toString(undefined, 0, 3));
// Prints: té
</code></pre>
<h3>buf.values()<span><a class="mark" href="#buffer_buf_values" id="buffer_buf_values">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v1.1.0</span>
</div><ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li>
</ul>
<p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> for <code>buf</code> values (bytes). This function is
called automatically when a <code>Buffer</code> is used in a <code>for..of</code> statement.</p>
<pre><code class="lang-js">const buf = Buffer.from('buffer');
for (const value of buf.values()) {
console.log(value);
}
// Prints:
// 98
// 117
// 102
// 102
// 101
// 114
for (const value of buf) {
console.log(value);
}
// Prints:
// 98
// 117
// 102
// 102
// 101
// 114
</code></pre>
<h3>buf.write(string[, offset[, length]][, encoding])<span><a class="mark" href="#buffer_buf_write_string_offset_length_encoding" id="buffer_buf_write_string_offset_length_encoding">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div><ul>
<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write <code>string</code>. <strong>Default:</strong> <code>0</code></li>
<li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. <strong>Default:</strong> <code>buf.length - offset</code></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The character encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes written.</li>
</ul>
<p>Writes <code>string</code> to <code>buf</code> at <code>offset</code> according to the character encoding in <code>encoding</code>.
The <code>length</code> parameter is the number of bytes to write. If <code>buf</code> did not contain
enough space to fit the entire string, only a partial amount of <code>string</code> will
be written. However, partially encoded characters will not be written.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(256);
const len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);
// Prints: 12 bytes: ½ + ¼ = ¾
</code></pre>
<h3>buf.writeDoubleBE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writedoublebe_value_offset_noassert" id="buffer_buf_writedoublebe_value_offset_noassert">#</a></span></h3>
<h3>buf.writeDoubleLE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writedoublele_value_offset_noassert" id="buffer_buf_writedoublele_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 8</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeDoubleBE()</code> writes big endian, <code>writeDoubleLE()</code> writes little
endian). <code>value</code> <em>should</em> be a valid 64-bit double. Behavior is undefined when
<code>value</code> is anything other than a 64-bit double.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(8);
buf.writeDoubleBE(0xdeadbeefcafebabe, 0);
console.log(buf);
// Prints: <Buffer 43 eb d5 b7 dd f9 5f d7>
buf.writeDoubleLE(0xdeadbeefcafebabe, 0);
console.log(buf);
// Prints: <Buffer d7 5f f9 dd b7 d5 eb 43>
</code></pre>
<h3>buf.writeFloatBE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writefloatbe_value_offset_noassert" id="buffer_buf_writefloatbe_value_offset_noassert">#</a></span></h3>
<h3>buf.writeFloatLE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writefloatle_value_offset_noassert" id="buffer_buf_writefloatle_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeFloatBE()</code> writes big endian, <code>writeFloatLE()</code> writes little
endian). <code>value</code> <em>should</em> be a valid 32-bit float. Behavior is undefined when
<code>value</code> is anything other than a 32-bit float.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(4);
buf.writeFloatBE(0xcafebabe, 0);
console.log(buf);
// Prints: <Buffer 4f 4a fe bb>
buf.writeFloatLE(0xcafebabe, 0);
console.log(buf);
// Prints: <Buffer bb fe 4a 4f>
</code></pre>
<h3>buf.writeInt8(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeint8_value_offset_noassert" id="buffer_buf_writeint8_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 1</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code>. <code>value</code> <em>should</em> be a valid
signed 8-bit integer. Behavior is undefined when <code>value</code> is anything other than
a signed 8-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<p><code>value</code> is interpreted and written as a two's complement signed integer.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(2);
buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);
console.log(buf);
// Prints: <Buffer 02 fe>
</code></pre>
<h3>buf.writeInt16BE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeint16be_value_offset_noassert" id="buffer_buf_writeint16be_value_offset_noassert">#</a></span></h3>
<h3>buf.writeInt16LE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeint16le_value_offset_noassert" id="buffer_buf_writeint16le_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 2</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeInt16BE()</code> writes big endian, <code>writeInt16LE()</code> writes little
endian). <code>value</code> <em>should</em> be a valid signed 16-bit integer. Behavior is undefined
when <code>value</code> is anything other than a signed 16-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<p><code>value</code> is interpreted and written as a two's complement signed integer.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(4);
buf.writeInt16BE(0x0102, 0);
buf.writeInt16LE(0x0304, 2);
console.log(buf);
// Prints: <Buffer 01 02 04 03>
</code></pre>
<h3>buf.writeInt32BE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeint32be_value_offset_noassert" id="buffer_buf_writeint32be_value_offset_noassert">#</a></span></h3>
<h3>buf.writeInt32LE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeint32le_value_offset_noassert" id="buffer_buf_writeint32le_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeInt32BE()</code> writes big endian, <code>writeInt32LE()</code> writes little
endian). <code>value</code> <em>should</em> be a valid signed 32-bit integer. Behavior is undefined
when <code>value</code> is anything other than a signed 32-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<p><code>value</code> is interpreted and written as a two's complement signed integer.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(8);
buf.writeInt32BE(0x01020304, 0);
buf.writeInt32LE(0x05060708, 4);
console.log(buf);
// Prints: <Buffer 01 02 03 04 08 07 06 05>
</code></pre>
<h3>buf.writeIntBE(value, offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_writeintbe_value_offset_bytelength_noassert" id="buffer_buf_writeintbe_value_offset_bytelength_noassert">#</a></span></h3>
<h3>buf.writeIntLE(value, offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_writeintle_value_offset_bytelength_noassert" id="buffer_buf_writeintle_value_offset_bytelength_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.11.15</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - byteLength</code>.</li>
<li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. Must satisfy: <code>0 < byteLength <= 6</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code>, <code>offset</code>, and <code>byteLength</code> validation?
<strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>byteLength</code> bytes of <code>value</code> to <code>buf</code> at the specified <code>offset</code>.
Supports up to 48 bits of accuracy. Behavior is undefined when <code>value</code> is
anything other than a signed integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(6);
buf.writeIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
buf.writeIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
</code></pre>
<h3>buf.writeUInt8(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeuint8_value_offset_noassert" id="buffer_buf_writeuint8_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 1</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code>. <code>value</code> <em>should</em> be a
valid unsigned 8-bit integer. Behavior is undefined when <code>value</code> is anything
other than an unsigned 8-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(4);
buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);
console.log(buf);
// Prints: <Buffer 03 04 23 42>
</code></pre>
<h3>buf.writeUInt16BE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeuint16be_value_offset_noassert" id="buffer_buf_writeuint16be_value_offset_noassert">#</a></span></h3>
<h3>buf.writeUInt16LE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeuint16le_value_offset_noassert" id="buffer_buf_writeuint16le_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 2</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeUInt16BE()</code> writes big endian, <code>writeUInt16LE()</code> writes little
endian). <code>value</code> should be a valid unsigned 16-bit integer. Behavior is
undefined when <code>value</code> is anything other than an unsigned 16-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(4);
buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);
console.log(buf);
// Prints: <Buffer de ad be ef>
buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);
console.log(buf);
// Prints: <Buffer ad de ef be>
</code></pre>
<h3>buf.writeUInt32BE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeuint32be_value_offset_noassert" id="buffer_buf_writeuint32be_value_offset_noassert">#</a></span></h3>
<h3>buf.writeUInt32LE(value, offset[, noAssert])<span><a class="mark" href="#buffer_buf_writeuint32le_value_offset_noassert" id="buffer_buf_writeuint32le_value_offset_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - 4</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code> and <code>offset</code> validation? <strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian
format (<code>writeUInt32BE()</code> writes big endian, <code>writeUInt32LE()</code> writes little
endian). <code>value</code> should be a valid unsigned 32-bit integer. Behavior is
undefined when <code>value</code> is anything other than an unsigned 32-bit integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(4);
buf.writeUInt32BE(0xfeedface, 0);
console.log(buf);
// Prints: <Buffer fe ed fa ce>
buf.writeUInt32LE(0xfeedface, 0);
console.log(buf);
// Prints: <Buffer ce fa ed fe>
</code></pre>
<h3>buf.writeUIntBE(value, offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_writeuintbe_value_offset_bytelength_noassert" id="buffer_buf_writeuintbe_value_offset_bytelength_noassert">#</a></span></h3>
<h3>buf.writeUIntLE(value, offset, byteLength[, noAssert])<span><a class="mark" href="#buffer_buf_writeuintle_value_offset_bytelength_noassert" id="buffer_buf_writeuintle_value_offset_bytelength_noassert">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v0.5.5</span>
</div><ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li>
<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy: <code>0 <= offset <= buf.length - byteLength</code>.</li>
<li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. Must satisfy: <code>0 < byteLength <= 6</code>.</li>
<li><code>noAssert</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Skip <code>value</code>, <code>offset</code>, and <code>byteLength</code> validation?
<strong>Default:</strong> <code>false</code></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li>
</ul>
<p>Writes <code>byteLength</code> bytes of <code>value</code> to <code>buf</code> at the specified <code>offset</code>.
Supports up to 48 bits of accuracy. Behavior is undefined when <code>value</code> is
anything other than an unsigned integer.</p>
<p>Setting <code>noAssert</code> to <code>true</code> allows the encoded form of <code>value</code> to extend beyond
the end of <code>buf</code>, but the resulting behavior is undefined.</p>
<pre><code class="lang-js">const buf = Buffer.allocUnsafe(6);
buf.writeUIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
buf.writeUIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
</code></pre>
<h2>buffer.INSPECT_MAX_BYTES<span><a class="mark" href="#buffer_buffer_inspect_max_bytes" id="buffer_buffer_inspect_max_bytes">#</a></span></h2>
<div class="api_metadata">
<span>Added in: v0.5.4</span>
</div><ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>50</code></li>
</ul>
<p>Returns the maximum number of bytes that will be returned when
<code>buf.inspect()</code> is called. This can be overridden by user modules. See
<a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a> for more details on <code>buf.inspect()</code> behavior.</p>
<p>Note that this is a property on the <code>buffer</code> module returned by
<code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p>
<h2>buffer.kMaxLength<span><a class="mark" href="#buffer_buffer_kmaxlength" id="buffer_buffer_kmaxlength">#</a></span></h2>
<div class="api_metadata">
<span>Added in: v3.0.0</span>
</div><ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest size allowed for a single <code>Buffer</code> instance.</li>
</ul>
<p>An alias for <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a></p>
<p>Note that this is a property on the <code>buffer</code> module returned by
<code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p>
<h2>buffer.transcode(source, fromEnc, toEnc)<span><a class="mark" href="#buffer_buffer_transcode_source_fromenc_toenc" id="buffer_buffer_transcode_source_fromenc_toenc">#</a></span></h2>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v8.0.0</td>
<td><p>The <code>source</code> parameter can now be a <code>Uint8Array</code>.</p>
</td></tr>
<tr><td>v7.1.0</td>
<td><p><span>Added in: v7.1.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li><code>source</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <code>Uint8Array</code> instance.</li>
<li><code>fromEnc</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The current encoding.</li>
<li><code>toEnc</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> To target encoding.</li>
</ul>
<p>Re-encodes the given <code>Buffer</code> or <code>Uint8Array</code> instance from one character
encoding to another. Returns a new <code>Buffer</code> instance.</p>
<p>Throws if the <code>fromEnc</code> or <code>toEnc</code> specify invalid character encodings or if
conversion from <code>fromEnc</code> to <code>toEnc</code> is not permitted.</p>
<p>The transcoding process will use substitution characters if a given byte
sequence cannot be adequately represented in the target encoding. For instance:</p>
<pre><code class="lang-js">const buffer = require('buffer');
const newBuf = buffer.transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'
</code></pre>
<p>Because the Euro (<code>€</code>) sign is not representable in US-ASCII, it is replaced
with <code>?</code> in the transcoded <code>Buffer</code>.</p>
<p>Note that this is a property on the <code>buffer</code> module returned by
<code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p>
<h2>Class: SlowBuffer<span><a class="mark" href="#buffer_class_slowbuffer" id="buffer_class_slowbuffer">#</a></span></h2>
<div class="api_metadata">
<span>Deprecated since: v6.0.0</span>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a> instead.</div><p>Returns an un-pooled <code>Buffer</code>.</p>
<p>In order to avoid the garbage collection overhead of creating many individually
allocated <code>Buffer</code> instances, by default allocations under 4KB are sliced from a
single larger allocated object.</p>
<p>In the case where a developer may need to retain a small chunk of memory from a
pool for an indeterminate amount of time, it may be appropriate to create an
un-pooled <code>Buffer</code> instance using <code>SlowBuffer</code> then copy out the relevant bits.</p>
<pre><code class="lang-js">// Need to keep around a few small chunks of memory
const store = [];
socket.on('readable', () => {
const data = socket.read();
// Allocate for retained data
const sb = SlowBuffer(10);
// Copy the data into the new allocation
data.copy(sb, 0, 0, 10);
store.push(sb);
});
</code></pre>
<p>Use of <code>SlowBuffer</code> should be used only as a last resort <em>after</em> a developer
has observed undue memory retention in their applications.</p>
<h3>new SlowBuffer(size)<span><a class="mark" href="#buffer_new_slowbuffer_size" id="buffer_new_slowbuffer_size">#</a></span></h3>
<div class="api_metadata">
<span>Deprecated since: v6.0.0</span>
</div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a> instead.</div><ul>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>SlowBuffer</code>.</li>
</ul>
<p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If the <code>size</code> is larger than
<a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, a <a href="errors.html#errors_class_rangeerror"><code>RangeError</code></a> will be
thrown. A zero-length <code>Buffer</code> will be created if <code>size</code> is 0.</p>
<p>The underlying memory for <code>SlowBuffer</code> instances is <em>not initialized</em>. The
contents of a newly created <code>SlowBuffer</code> are unknown and may contain sensitive
data. Use <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> to initialize a <code>SlowBuffer</code> with
zeroes.</p>
<pre><code class="lang-js">const { SlowBuffer } = require('buffer');
const buf = new SlowBuffer(5);
console.log(buf);
// Prints: (contents may vary): <Buffer 78 e0 82 02 01>
buf.fill(0);
console.log(buf);
// Prints: <Buffer 00 00 00 00 00>
</code></pre>
<h2>Buffer Constants<span><a class="mark" href="#buffer_buffer_constants" id="buffer_buffer_constants">#</a></span></h2>
<div class="api_metadata">
<span>Added in: v8.2.0</span>
</div><p>Note that <code>buffer.constants</code> is a property on the <code>buffer</code> module returned by
<code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p>
<h3>buffer.constants.MAX_LENGTH<span><a class="mark" href="#buffer_buffer_constants_max_length" id="buffer_buffer_constants_max_length">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v8.2.0</span>
</div><ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest size allowed for a single <code>Buffer</code> instance.</li>
</ul>
<p>On 32-bit architectures, this value is <code>(2^30)-1</code> (~1GB).
On 64-bit architectures, this value is <code>(2^31)-1</code> (~2GB).</p>
<p>This value is also available as <a href="#buffer_buffer_kmaxlength"><code>buffer.kMaxLength</code></a>.</p>
<h3>buffer.constants.MAX_STRING_LENGTH<span><a class="mark" href="#buffer_buffer_constants_max_string_length" id="buffer_buffer_constants_max_string_length">#</a></span></h3>
<div class="api_metadata">
<span>Added in: v8.2.0</span>
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<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest length allowed for a single <code>string</code> instance.</li>
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<p>Represents the largest <code>length</code> that a <code>string</code> primitive can have, counted
in UTF-16 code units.</p>
<p>This value may depend on the JS engine that is being used.</p>
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