Revision 944017 of Float64Array

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

<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">
new Float64Array(length);
new Float64Array(typedArray);
new Float64Array(object);
new 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>Static length property whose value is 3. For the actual length (number of elements), see {{jsxref("TypedArray.prototype.length", "Float64Array.prototype.length")}}.</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>{{jsxref("TypedArray.from", "Float64Array.from()")}}</dt>
 <dd>Creates a new <code>Float64Array</code> from an array-like or iterable object. See also {{jsxref("Array.from()")}}.</dd>
 <dt>{{jsxref("TypedArray.of", "Float64Array.of()")}}</dt>
 <dd>Creates a new <code>Float64Array</code> with a variable number of arguments. See also {{jsxref("Array.of()")}}.</dd>
</dl>

<h2 id="Float64Array_prototype"><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.copyWithin", "Float64Array.prototype.copyWithin()")}}</dt>
 <dd>Copies a sequence of array elements within the array. See also {{jsxref("Array.prototype.copyWithin()")}}.</dd>
 <dt>{{jsxref("TypedArray.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. See also {{jsxref("Array.prototype.entries()")}}.</dd>
 <dt>{{jsxref("TypedArray.every", "Float64Array.prototype.every()")}}</dt>
 <dd>Tests whether all elements in the array pass the test provided by a function. See also {{jsxref("Array.prototype.every()")}}.</dd>
 <dt>{{jsxref("TypedArray.fill", "Float64Array.prototype.fill()")}}</dt>
 <dd>Fills all the elements of an array from a start index to an end index with a static value. See also {{jsxref("Array.prototype.fill()")}}.</dd>
 <dt>{{jsxref("TypedArray.filter", "Float64Array.prototype.filter()")}}</dt>
 <dd>Creates a new array with all of the elements of this array for which the provided filtering function returns true. See also {{jsxref("Array.prototype.filter()")}}.</dd>
 <dt>{{jsxref("TypedArray.find", "Float64Array.prototype.find()")}}</dt>
 <dd>Returns the found value in the array, if an element in the array satisfies the provided testing function or <code>undefined</code> if not found. See also {{jsxref("Array.prototype.find()")}}.</dd>
 <dt>{{jsxref("TypedArray.findIndex", "Float64Array.prototype.findIndex()")}}</dt>
 <dd>Returns the found index in the array, if an element in the array satisfies the provided testing function or -1 if not found. See also {{jsxref("Array.prototype.findIndex()")}}.</dd>
 <dt>{{jsxref("TypedArray.forEach", "Float64Array.prototype.forEach()")}}</dt>
 <dd>Calls a function for each element in the array. See also {{jsxref("Array.prototype.forEach()")}}.</dd>
 <dt>{{jsxref("TypedArray.includes", "Float64Array.prototype.includes()")}} {{experimental_inline}}</dt>
 <dd>Determines whether a typed array includes a certain element, returning <code>true</code> or <code>false</code> as appropriate. See also {{jsxref("Array.prototype.includes()")}}.</dd>
 <dt>{{jsxref("TypedArray.indexOf", "Float64Array.prototype.indexOf()")}}</dt>
 <dd>Returns the first (least) index of an element within the array equal to the specified value, or -1 if none is found. See also {{jsxref("Array.prototype.indexOf()")}}.</dd>
 <dt>{{jsxref("TypedArray.join", "Float64Array.prototype.join()")}}</dt>
 <dd>Joins all elements of an array into a string. See also {{jsxref("Array.prototype.join()")}}.</dd>
 <dt>{{jsxref("TypedArray.keys", "Float64Array.prototype.keys()")}}</dt>
 <dd>Returns a new <code>Array Iterator</code> that contains the keys for each index in the array. See also {{jsxref("Array.prototype.keys()")}}.</dd>
 <dt>{{jsxref("TypedArray.lastIndexOf", "Float64Array.prototype.lastIndexOf()")}}</dt>
 <dd>Returns the last (greatest) index of an element within the array equal to the specified value, or -1 if none is found. See also {{jsxref("Array.prototype.lastIndexOf()")}}.</dd>
 <dt>{{jsxref("TypedArray.map", "Float64Array.prototype.map()")}}</dt>
 <dd>Creates a new array with the results of calling a provided function on every element in this array. See also {{jsxref("Array.prototype.map()")}}.</dd>
 <dt>{{jsxref("TypedArray.move", "Float64Array.prototype.move()")}} {{non-standard_inline}} {{unimplemented_inline}}</dt>
 <dd>Former non-standard version of {{jsxref("TypedArray.copyWithin", "Float64Array.prototype.copyWithin()")}}.</dd>
 <dt>{{jsxref("TypedArray.reduce", "Float64Array.prototype.reduce()")}}</dt>
 <dd>Apply a function against an accumulator and each value of the array (from left-to-right) as to reduce it to a single value. See also {{jsxref("Array.prototype.reduce()")}}.</dd>
 <dt>{{jsxref("TypedArray.reduceRight", "Float64Array.prototype.reduceRight()")}}</dt>
 <dd>Apply a function against an accumulator and each value of the array (from right-to-left) as to reduce it to a single value. See also {{jsxref("Array.prototype.reduceRight()")}}.</dd>
 <dt>{{jsxref("TypedArray.reverse", "Float64Array.prototype.reverse()")}}</dt>
 <dd>Reverses the order of the elements of an array&nbsp;— the first becomes the last, and the last becomes the first. See also {{jsxref("Array.prototype.reverse()")}}.</dd>
 <dt>{{jsxref("TypedArray.set", "Float64Array.prototype.set()")}}</dt>
 <dd>Stores multiple values in the typed array, reading input values from a specified array.</dd>
 <dt>{{jsxref("TypedArray.slice", "Float64Array.prototype.slice()")}}</dt>
 <dd>Extracts a section of an array and returns a new array. See also {{jsxref("Array.prototype.slice()")}}.</dd>
 <dt>{{jsxref("TypedArray.some", "Float64Array.prototype.some()")}}</dt>
 <dd>Returns true if at least one element in this array satisfies the provided testing function. See also {{jsxref("Array.prototype.some()")}}.</dd>
 <dt>{{jsxref("TypedArray.sort", "Float64Array.prototype.sort()")}}</dt>
 <dd>Sorts the elements of an array in place and returns the array. See also {{jsxref("Array.prototype.sort()")}}.</dd>
 <dt>{{jsxref("TypedArray.subarray", "Float64Array.prototype.subarray()")}}</dt>
 <dd>Returns a new <code>Float64Array</code> from the given start and end element index.</dd>
 <dt>{{jsxref("TypedArray.values", "Float64Array.prototype.values()")}}</dt>
 <dd>Returns a new <code>Array Iterator</code> object that contains the values for each index in the array. See also {{jsxref("Array.prototype.values()")}}.</dd>
 <dt>{{jsxref("TypedArray.toLocaleString", "Float64Array.prototype.toLocaleString()")}}</dt>
 <dd>Returns a localized string representing the array and its elements. See also {{jsxref("Array.prototype.toLocaleString()")}}.</dd>
 <dt>{{jsxref("TypedArray.toString", "Float64Array.prototype.toString()")}}</dt>
 <dd>Returns a string representing the array and its elements. See also {{jsxref("Array.prototype.toString()")}}.</dd>
 <dt>{{jsxref("TypedArray.@@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>{{SpecName('Typed Array')}}</td>
   <td>{{Spec2('Typed Array')}}</td>
   <td>Superseded by ECMAScript 6.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#table-49', 'TypedArray constructors')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition in an ECMA standard. Specified that <code>new</code> is required.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#table-49', 'TypedArray constructors')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td>&nbsp;</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>
  <tr>
   <td><code>new</code> is required</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoDesktop(44)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</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>
  <tr>
   <td><code>new</code> is required</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{ CompatGeckoMobile(44) }}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

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

<p>Starting with ECMAScript 2015 (ES6), <code>Float64Array</code> constructors require to be constructed with a {{jsxref("Operators/new", "new")}} operator. Calling a <code>Float64Array</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 = Float64Array([1, 2, 3]);
// TypeError: calling a builtin Float64Array constructor
// without new is forbidden</pre>

<pre class="brush: js example-good">
var dv = new Float64Array([1, 2, 3]);</pre>

<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>