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

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<p><strong><code>Number.isFinite()</code></strong> 方法用来检测传入的参数是否是一个有穷数（finite number）。</p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre><code class="language-javascript"><code>Number.isFinite(v<var>alue</var>)</code></code></pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>value</code></dt>
<dd>要被检测有穷性的值。</dd>
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<h3 id="返回值">返回值</h3>
<p>一个 <a href="Reference/Boolean" title="此页面仍未被本地化, 期待您的翻译!"><code>布尔值</code></a> 表示给定的值是否是一个有穷数。</p>
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<h2 id="描述">描述</h2>
<p>和全局的 <a href="Reference/Global_Objects/isFinite" title="该全局 isFinite() 函数用来判断被传入的参数值是否为一个有限数值（finite number）。在必要情况下，参数会首先转为一个数值。"><code>isFinite()</code></a> 函数相比，这个方法不会强制将一个非数值的参数转换成数值，这就意味着，只有数值类型的值，且是有穷的（finite），才返回 <code>true</code>。</p>
<h2 id="示例">示例</h2>
<pre><code  class="language-javascript">Number.isFinite(Infinity);  // false
Number.isFinite(NaN);       // false
Number.isFinite(-Infinity); // false

Number.isFinite(0);         // true
Number.isFinite(2e64);      // true

Number.isFinite('0');       // false, 全局函数 isFinite('0') 会返回 true
</code></pre>
<h2 id="Polyfill">Polyfill</h2>
<pre><code  class="language-javascript">Number.isFinite = Number.isFinite || function(value) {
    return typeof value === "number" &amp;&amp; isFinite(value);
}
</code></pre>
<h2 id="规范">规范</h2>
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<th scope="col">规范名称</th>
<th scope="col">规范状态</th>
<th scope="col">备注</th>
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<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-number.isfinite" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Number.isInteger</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-number.isfinite" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Number.isInteger</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
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<h2 id="Browser_compatibility" name="Browser_compatibility">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>.
            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>
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<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
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<th>Feature</th>
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<th>Firefox (Gecko)</th>
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<td>Basic support</td>
<td>19</td>
<td><a href="/en-US/Firefox/Releases/16" title="Released on 2012-10-09.">16</a> (16)</td>
<td><span style="color: #f00;">未实现</span></td>
<td>15</td>
<td>9</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: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td>16.0 (16)</td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li><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></li>
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