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---
title: DataView.prototype.getFloat64()
slug: Web/JavaScript/Reference/Global_Objects/DataView/getFloat64
translation_of: Web/JavaScript/Reference/Global_Objects/DataView/getFloat64
---
<div>{{JSRef}}</div>
<p><strong><code>getFloat64()</code></strong><code>方法</code><code>从</code><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/DataView" title="DataView 视图提供了一种用于向 ArrayBuffer 读写数据的底层接口。"><code>DataView</code></a>相对于起始位置偏移 n 个字节处开始，获取一个64-bit数(双精度浮点型，8个字节).</p>
<div>{{EmbedInteractiveExample("pages/js/dataview-getfloat64.html")}}</div>
<h2 id="语法">语法</h2>
<pre class="syntaxbox"><var>dataview</var>.getFloat64(byteOffset [, littleEndian])</pre>
<h3 id="参数">参数</h3>
<dl>
<dt>byteOffset</dt>
<dd>偏移量, 单位为字节, 从头开始计算.</dd>
<dt>littleEndian</dt>
<dd>{{optional_inline}} Indicates whether the 64-bit float is stored in {{Glossary("Endianness", "little- or big-endian")}} format. If false or undefined, a big-endian value is read.</dd>
</dl>
<h3 id="返回">返回</h3>
<dl>
<dd>一个双精度浮点型64位数.</dd>
</dl>
<h3 id="抛出错误">抛出错误</h3>
<dl>
<dt>{{jsxref("RangeError")}}</dt>
<dd>如果byteOffset超出了视图能储存的值，就会抛出错误.</dd>
</dl>
<h2 id="描述">描述</h2>
<dl>
<dd>没有对齐约束; 多字节值可以从任何偏移量获取.</dd>
</dl>
<h2 id="例子">例子</h2>
<pre class="brush:js">var buffer = new ArrayBuffer(8);
var dataview = new DataView(buffer);
dataview.getFloat64(1); // 0
</pre>
<h2 id="规范">规范</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Superseded by ECMAScript 6.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-dataview.prototype.getfloat64', 'DataView.prototype.getFloat64')}}</td>
<td>{{Spec2('ES6')}}</td>
<td>Initial definition in ECMA standard.</td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-dataview.prototype.getfloat64', 'DataView.prototype.getFloat64')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td></td>
</tr>
</tbody>
</table>
<h2 id="浏览器支持">浏览器支持</h2>
<p>{{Compat("javascript.builtins.DataView.getFloat64")}}</p>
<h2 id="另见">另见</h2>
<ul>
<li>{{jsxref("DataView")}}</li>
<li>{{jsxref("ArrayBuffer")}}</li>
</ul>
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