uTools-Manuals/docs/javascript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER.html

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<p><strong><code>Number.MAX_SAFE_INTEGER</code></strong> 常量表示在 JavaScript 中最大的安全整数（maxinum safe integer)（<code>2<sup>53</sup> - 1）。</code></p>
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<th class="header" colspan="2"><code>Number.MAX_SAFE_INTEGER</code> 属性的属性特性：</th>
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<td>writable</td>
<td>false</td>
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<td>enumerable</td>
<td>false</td>
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<td>configurable</td>
<td>false</td>
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<h2 id="描述">描述</h2>
<p><code>MAX_SAFE_INTEGER 是一个值为 9007199254740991的常量。因为Javascript的数字存储使用了</code><a class="external" href="http://en.wikipedia.org/wiki/IEEE_floating_point" rel="noopener">IEEE 754</a>中规定的<a class="external" href="https://zh.wikipedia.org/zh-cn/%E9%9B%99%E7%B2%BE%E5%BA%A6%E6%B5%AE%E9%BB%9E%E6%95%B8" rel="noopener">双精度浮点数</a>数据类型，而这一数据类型能够安全存储 <code>-(2<sup>53</sup> - 1)</code> 到 <code>2<sup>53</sup> - 1 之间的数值（包含边界值）。</code></p>
<p>这里安全存储的意思是指能够准确区分两个不相同的值，例如 <code>Number.MAX_SAFE_INTEGER + 1 === Number.MAX_SAFE_INTEGER + 2 将得到 true的结果，而这在数学上是错误的，参考</code><a href="Reference/Global_Objects/Number/isSafeInteger" title="Number.isSafeInteger() 方法用来判断传入的参数值是否是一个“安全整数”（safe integer）。一个安全整数是一个符合下面条件的整数："><code>Number.isSafeInteger()</code></a>获取更多信息.</p>
<p>由于 <code>MAX_SAFE_INTEGER 是</code><a href="Reference/Global_Objects/Number" title="JavaScript 的 Number 对象是经过封装的能让你处理数字值的对象。Number 对象由 Number() 构造器创建。"><code>Number</code></a>的一个<code>静态属性，所以你不用自己动手为</code><a href="Reference/Global_Objects/Number" title="JavaScript 的 Number 对象是经过封装的能让你处理数字值的对象。Number 对象由 Number() 构造器创建。"><code>Number</code></a>对象创建<code>Number.MAX_SAFE_INTEGER</code>这一属性，就可以直接使用它。</p>
<h2 id="示例">示例</h2>
<pre><code  class="language-javascript">Number.MAX_SAFE_INTEGER // 9007199254740991
Math.pow(2, 53) - 1     // 9007199254740991
</code></pre>
<h2 id="规范">规范</h2>
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<th scope="col">Specification</th>
<th scope="col">Status</th>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-number.max_safe_integer" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Number.MAX_SAFE_INTEGER</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>首次定义</td>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-number.max_safe_integer" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Number.MAX_SAFE_INTEGER</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
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<h2 id="浏览器兼容性">浏览器兼容性</h2>
<div><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
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            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
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<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
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<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
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<td>Basic support</td>
<td>34</td>
<td><a href="/en-US/Firefox/Releases/31" title="Released on 2014-07-22.">31</a> (31)</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td>9.0.2</td>
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<td>Basic support</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td>32.0 (32)</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
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<h2 id="相关链接">相关链接</h2>
<ul>
<li><a href="Reference/Global_Objects/Number/MIN_SAFE_INTEGER" title="Number.MIN_SAFE_INTEGER 代表在 JavaScript中最小的安全的integer型数字 (-(253 - 1))."><code>Number.MIN_SAFE_INTEGER</code></a></li>
<li><a href="Reference/Global_Objects/Number/isSafeInteger" title="Number.isSafeInteger() 方法用来判断传入的参数值是否是一个“安全整数”（safe integer）。一个安全整数是一个符合下面条件的整数："><code>Number.isSafeInteger()</code></a></li>
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