Revision 703209 of Float64Array

<div>
 {{JSRef("Global_Objects", "TypedArray", "Int8Array,Uint8Array,Uint8ClampedArray,Int16Array,Uint16Array,Int32Array,Uint32Array,Float32Array,Float64Array")}}</div>
<h2 id="Summary">Summary</h2>
<p>The <strong><code>Float64Array</code></strong> typed array represents an array of 64-bit floating point numbers (corresponding to the C <code>double</code> data type) in the platform byte order. If control over byte order is needed, use {{jsxref("DataView")}} instead. The contents are initialized to <code>0</code>. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).</p>
<h2 id="Syntax">Syntax</h2>
<pre class="syntaxbox">
Float64Array(length);
Float64Array(typedArray);
Float64Array(object);
Float64Array(buffer [, byteOffset [, length]]);</pre>
<p>For more information about the constructor syntax and the parameters, see <em><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray#Syntax">TypedArray</a></em>.</p>
<h2 id="Properties">Properties</h2>
<dl>
 <dt>
  {{jsxref("TypedArray.BYTES_PER_ELEMENT", "Float64Array.BYTES_PER_ELEMENT")}}</dt>
 <dd>
  Returns a number value of the element size. <code>8</code> in the case of an <code>Float64Array</code>.</dd>
 <dt>
  Float64Array.length</dt>
 <dd>
  Length property whose value is 3.</dd>
 <dt>
  {{jsxref("TypedArray.name", "Float64Array.name")}}</dt>
 <dd>
  Returns the string value of the constructor name. In the case of the <code>Float64Array</code> type: "Float64Array".</dd>
 <dt>
  {{jsxref("TypedArray.prototype", "Float64Array.prototype")}}</dt>
 <dd>
  Prototype for the <em>TypedArray</em> objects.</dd>
</dl>
<h2 id="Methods">Methods</h2>
<dl>
 <dt>
  Float64Array.from()</dt>
 <dd>
  See {{jsxref("Array.from()")}}. Not implemented, see {{bug(896608)}}.</dd>
 <dt>
  Float64Array.of()</dt>
 <dd>
  See {{ jsxref("Array.of()")}}. Not implemented, see {{bug(896608)}}.</dd>
</dl>
<h2 id="Boolean_instances" name="Boolean_instances"><code>Float64Array</code> prototype</h2>
<p>All <code>Float64Array</code> objects inherit from {{jsxref("TypedArray.prototype", "%TypedArray%.prototype")}}.</p>
<h3 id="Properties_2">Properties</h3>
<dl>
 <dt>
  <code>Float64Array.prototype.constructor</code></dt>
 <dd>
  Returns the function that created an instance's prototype. This is the <code>Float64Array</code> constructor by default.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.buffer", "Float64Array.prototype.buffer")}} {{readonlyInline}}</dt>
 <dd>
  Returns the {{jsxref("ArrayBuffer")}} referenced by the <code>Float64Array</code> Fixed at construction time and thus <strong>read only</strong>.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.byteLength", "Float64Array.prototype.byteLength")}} {{readonlyInline}}</dt>
 <dd>
  Returns the length (in bytes) of the <code>Float64Array</code> from the start of its {{jsxref("ArrayBuffer")}}. Fixed at construction time and thus <strong>read only.</strong></dd>
 <dt>
  {{jsxref("TypedArray.prototype.byteOffset", "Float64Array.prototype.byteOffset")}} {{readonlyInline}}</dt>
 <dd>
  Returns the offset (in bytes) of the <code>Float64Array</code> from the start of its {{jsxref("ArrayBuffer")}}. Fixed at construction time and thus <strong>read only.</strong></dd>
 <dt>
  {{jsxref("TypedArray.prototype.length", "Float64Array.prototype.length")}} {{readonlyInline}}</dt>
 <dd>
  Returns the number of elements hold in the <code>Float64Array</code>. Fixed at construction time and thus <strong>read only.</strong></dd>
</dl>
<h3 id="Methods_2">Methods</h3>
<dl>
 <dt>
  {{jsxref("TypedArray.prototype.copyWithin()", "Float64Array.prototype.copyWithin()")}}</dt>
 <dd>
  See {{jsxref("Array.prototype.copyWithin()")}}.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.entries()", "Float64Array.prototype.entries()")}}</dt>
 <dd>
  Returns a new <code>Array Iterator</code> object that contains the key/value pairs for each index in the array.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.keys()", "Float64Array.prototype.keys()")}}</dt>
 <dd>
  Returns a new <code>Array Iterator</code> that contains the keys for each index in the array.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.move()", "Float64Array.prototype.move()")}} {{non-standard_inline}} {{unimplemented_inline}}</dt>
 <dd>
  Former non-standard version of {{jsxref("TypedArray.prototype.copyWithin()", "Float64Array.prototype.copyWithin()")}}.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.set()", "Float64Array.prototype.set()")}}</dt>
 <dd>
  Stores multiple values in the <code>Float64Array</code>, reading input values from a specified array.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.subarray()", "Float64Array.prototype.subarray()")}}</dt>
 <dd>
  Returns a new <code>Float64Array</code> from the given start and end element index.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.values()", "Float64Array.prototype.values()")}}</dt>
 <dd>
  Returns a new <code>Array Iterator</code> object that contains the values for each index in the array.</dd>
 <dt>
  {{jsxref("TypedArray.prototype.@@iterator()", "Float64Array.prototype[@@iterator]()")}}</dt>
 <dd>
  Returns a new <code>Array Iterator</code> object that contains the values for each index in the array.</dd>
</dl>
<h2 id="Examples">Examples</h2>
<pre class="brush: js">
// From a length
var float64 = new Float64Array(2);
float64[0] = 42;
console.log(float64[0]); // 42
console.log(float64.length); // 2
console.log(float64.BYTES_PER_ELEMENT); // 8

// From an array
var arr = new Float64Array([21,31]);
console.log(arr[1]); // 31

// From another TypedArray
var x = new Float64Array([21, 31]);
var y = new Float64Array(x);
console.log(y[0]); // 21

// From an ArrayBuffer
var buffer = new ArrayBuffer(32);
var z = new Float64Array(buffer, 0, 4);
</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><a href="https://www.khronos.org/registry/typedarray/specs/latest/#7">Typed Array Specification</a></td>
   <td>Obsolete</td>
   <td><span><span>Superseded by ECMAScript 6.</span></span></td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#table-45', 'TypedArray constructors')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition in an ECMA standard.</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="See_also">See also</h2>
<ul>
 <li><a href="/en-US/docs/Web/JavaScript/Typed_arrays" title="en/JavaScript typed arrays">JavaScript typed arrays</a></li>
 <li>{{jsxref("ArrayBuffer")}}</li>
 <li>{{jsxref("DataView")}}</li>
</ul>