Revision 943915 of ArrayBuffer

<div>{{JSRef}}</div>

<p>The <strong><code>ArrayBuffer</code></strong> object is used to represent a generic, fixed-length raw binary data buffer. You can not directly manipulate the contents of an <code>ArrayBuffer</code>; instead, you create one of the <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray">typed array objects</a> or a {{jsxref("DataView")}} object which represents the buffer in a specific format, and use that to read and write the contents of the buffer.</p>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">
new ArrayBuffer(length)
</pre>

<h3 id="Parameters">Parameters</h3>

<dl>
 <dt><code>length</code></dt>
 <dd>The size, in bytes, of the array buffer to create.</dd>
</dl>

<h3 id="Return_value">Return value</h3>

<p>A new <code>ArrayBuffer</code> object of the specified size. Its contents are initialized to 0.</p>

<h2 id="Description">Description</h2>

<p>The <code>ArrayBuffer</code> constructor creates a new <code>ArrayBuffer</code> of the given length in bytes.</p>

<h3 id="Getting_an_array_buffer_from_existing_data">Getting an array buffer from existing data</h3>

<ul>
 <li><a href="/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding#Appendix.3A_Decode_a_Base64_string_to_Uint8Array_or_ArrayBuffer">From a Base64 string</a></li>
 <li><a href="/en-US/docs/Web/API/FileReader#readAsArrayBuffer()">From a local file</a></li>
</ul>

<h2 id="Properties">Properties</h2>

<dl>
 <dt><code>ArrayBuffer.length</code></dt>
 <dd>The <code>ArrayBuffer</code> constructor's length property whose value is 1.</dd>
 <dt>{{jsxref("ArrayBuffer.prototype")}}</dt>
 <dd>Allows the addition of properties to all <code>ArrayBuffer</code> objects.</dd>
</dl>

<h2 id="Methods">Methods</h2>

<dl>
 <dt>{{jsxref("ArrayBuffer.isView", "ArrayBuffer.isView(arg)")}}</dt>
 <dd>Returns <code>true</code> if <code>arg</code> is one of the ArrayBuffer views, such as <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray">typed array objects</a> or a {{jsxref("DataView")}}. Returns <code>false</code> otherwise.</dd>
 <dt>{{jsxref("ArrayBuffer.transfer", "ArrayBuffer.transfer(oldBuffer [, newByteLength])")}} {{experimental_inline}}</dt>
 <dd>
 <div class="line" id="file-arraybuffer-transfer-LC6">Returns a new <code>ArrayBuffer</code> whose contents are taken from the <code>oldBuffer</code>'s data and then is either truncated or zero-extended by <code>newByteLength</code>.</div>
 </dd>
</dl>

<h2 id="ArrayBuffer_instances"><code>ArrayBuffer</code> instances</h2>

<p>All <code>ArrayBuffer</code> instances inherit from {{jsxref("ArrayBuffer.prototype")}}.</p>

<h3 id="Properties_2">Properties</h3>

<p>{{page('en-US/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/prototype','Properties')}}</p>

<h3 id="Methods_2">Methods</h3>

<p>{{page('en-US/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/prototype','Methods')}}</p>

<h2 id="Example">Example</h2>

<p>In this example, we create a 8-byte buffer with a {{jsxref("Global_Objects/Int32Array", "Int32Array")}} view referring to the buffer:</p>

<pre class="brush: js">
var buffer = new ArrayBuffer(8);
var view   = new Int32Array(buffer);</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('Typed Array')}}</td>
   <td>{{Spec2('Typed Array')}}</td>
   <td>Superseded by ECMAScript 6.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-arraybuffer-constructor', 'ArrayBuffer')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition in an ECMA standard. Specified that <code>new</code> is required.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>7.0</td>
   <td>{{CompatGeckoDesktop("2")}}</td>
   <td>10</td>
   <td>11.6</td>
   <td>5.1</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>4.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile("2")}}</td>
   <td>10</td>
   <td>11.6</td>
   <td>4.2</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="Firefox-specific_notes">Firefox-specific notes</h2>

<p>Starting with Gecko / SpiderMonkey 44 {{geckoRelease(44)}}, <code>ArrayBuffer</code> constructors require to be constructed with a {{jsxref("Operators/new", "new")}} operator. Calling an <code>ArrayBuffer</code> constructor as a function without <code>new</code>, will throw a {{jsxref("TypeError")}} from now on.</p>

<pre class="brush: js example-bad">
var dv = ArrayBuffer(10);
// TypeError: calling a builtin ArrayBuffer constructor 
// without new is forbidden</pre>

<pre class="brush: js example-good">
var dv = new ArrayBuffer(10);</pre>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/en-US/docs/Web/JavaScript/Typed_arrays">JavaScript typed arrays</a></li>
</ul>