uTools-Manuals/docs/javascript/Reference/Global_Objects/Infinity.html

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<p>全局属性 <code><strong>Infinity</strong></code> 是一个数值，表示无穷大。</p>
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<th class="header" colspan="2"><code>Infinity</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="Syntax" name="Syntax">语法</h2>
<pre><code class="language-javascript"><code>Infinity </code></code></pre>
<h2 id="Description" name="Description">描述</h2>
<p><code>Infinity</code> 是全局对象（<em>global object</em>）的一个属性，即它是一个全局变量。</p>
<p><code>Infinity</code> 的初始值是 <a href="Reference/Global_Objects/Number/POSITIVE_INFINITY" title="Number.POSITIVE_INFINITY 属性表示正无穷大。"><code>Number.POSITIVE_INFINITY</code></a>。<code>Infinity</code>（正无穷大）大于任何值。该值和数学意义上的无穷大很像，例如任何正值乘以 <code>Infinity</code> 为 <code>Infinity</code>, 任何数值（除了Infinity 和 -Infinity）除以 <code>Infinity</code> 为 0。</p>
<p>在 ECMAScript 5 的规范中， <code>Infinity</code> 是只读的（实现于 JavaScript 1.8.5 / Firefox 4）。</p>
<h2 id="示例">示例</h2>
<pre><code  class="language-javascript"><code class="language-js">console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span><span class="number token">Infinity</span>          <span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">/* Infinity */</span>  
console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span><span class="number token">Infinity</span> <span class="operator token">+</span> <span class="number token">1</span>      <span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">/* Infinity */</span>  
console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span>Math<span class="punctuation token">.</span><span class="function token">pow</span><span class="punctuation token">(</span><span class="number token">10</span><span class="punctuation token">,</span> <span class="number token">1000</span><span class="punctuation token">)</span><span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">/* Infinity */</span>  
console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span>Math<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span><span class="number token">0</span><span class="punctuation token">)</span>       <span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">/* -Infinity */</span>  
console<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span><span class="number token">1</span> <span class="operator token">/</span> <span class="number token">Infinity</span>      <span class="punctuation token">)</span><span class="punctuation token">;</span> <span class="comment token">/* 0 */</span></code></code></pre>
<h2 id="规范">规范</h2>
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<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
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<td><a class="external" href="https://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,%201st%20edition,%20June%201997.pdf" hreflang="en" lang="en" rel="noopener" title="ECMAScript 1st Edition (ECMA-262)">ECMAScript 1st Edition (ECMA-262)</a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition. Implemented in JavaScript 1.3</td>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.1.1.2" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">Infinity</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-value-properties-of-the-global-object-infinity" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Infinity</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-value-properties-of-the-global-object-infinity" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Infinity</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>
<p></p><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>.
            This compatibility table still uses the old format,
            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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<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<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>
<th>Internet Explorer</th>
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<th>Safari</th>
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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><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><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<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>
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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><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><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>
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<h2 id="相关链接">相关链接</h2>
<ul>
<li><a href="Reference/Global_Objects/Number/NEGATIVE_INFINITY" title="Number.NEGATIVE_INFINITY 属性表示负无穷大。"><code>Number.NEGATIVE_INFINITY</code></a></li>
<li><a href="Reference/Global_Objects/Number/POSITIVE_INFINITY" title="Number.POSITIVE_INFINITY 属性表示正无穷大。"><code>Number.POSITIVE_INFINITY</code></a></li>
<li><a href="Reference/Global_Objects/Number/isFinite" title="Number.isFinite() 方法用来检测传入的参数是否是一个有穷数（finite number）。"><code>Number.isFinite</code></a></li>
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