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---
title: isFinite()
slug: Web/JavaScript/Reference/Global_Objects/isFinite
tags:
- JavaScript
- isFinite
translation_of: Web/JavaScript/Reference/Global_Objects/isFinite
---
<div>{{jsSidebar("Objects")}}</div>
<p>该全局 <strong><code>isFinite()</code></strong> 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。</p>
<div>{{EmbedInteractiveExample("pages/js/globalprops-isfinite.html")}}</div>
<h2 id="语法">语法</h2>
<pre class="syntaxbox language-html" style="margin-bottom: 0px; padding: 1em; border-left-width: 6px; border-left-style: solid; font-family: Consolas, Monaco, 'Andale Mono', monospace; font-size: 14px; direction: ltr; white-space: normal; text-shadow: none; background-color: rgba(212, 221, 228, 0.498039);">isFinite(<em>testValue</em>)</pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>testValue</code></dt>
<dd>用于检测有限性（finiteness）的值。</dd>
</dl>
<h3 id="Description" name="Description">描述</h3>
<dl>
<dd>isFinite 是全局的方法，不与任何对象有关系。</dd>
</dl>
<p>你可以用这个方法来判定一个数字是否是有限数字。<code>isFinite</code> 方法检测它参数的数值。如果参数是 <code>NaN</code>，正无穷大或者负无穷大，会返回<code>false</code>，其他返回 <code>true</code>。</p>
<h2 id="Examples" name="Examples" style="margin-bottom: 20px; line-height: 30px;">示例</h2>
<pre class="brush: js language-js" style="padding: 1em 0px 1em 30px; border-left-width: 6px; border-left-style: solid; font-family: Consolas, Monaco, 'Andale Mono', monospace; font-size: 14px; direction: ltr; white-space: normal; text-shadow: none; background-color: rgba(234, 239, 242, 0.247059);"><code class="language-js" style="font-family: Consolas, Monaco, 'Andale Mono', monospace; direction: ltr; white-space: pre; color: inherit; text-shadow: none;"><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">Infinity</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // false
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">NaN</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // false
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="operator token" style="background: rgba(255, 255, 255, 0.498039); color: #a67f59;">-</span><span class="number token" style="color: #990055;">Infinity</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span><span class="comment token" style="color: #708090; display: inherit;"> // false
</span>
<span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">0</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // true
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">2e64</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // true, 在更强壮的Number.isFinite(null)中将会得到false
</span>
<span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="string token" style="color: #669900;">"0"</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // true, 在更强壮的Number.isFinite('0')中将会得到false</span></code></pre>
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<h2 id="规范" style="margin-bottom: 20px; line-height: 30px;">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('ES3')}}</td>
<td>{{Spec2('ES3')}}</td>
<td>Initial definition.</td>
</tr>
<tr>
<td>{{SpecName('ES5.1', '#sec-15.1.2.5', 'isFinite')}}</td>
<td>{{Spec2('ES5.1')}}</td>
<td> </td>
</tr>
<tr>
<td>{{SpecName('ES6', '#sec-isfinite-number', 'isFinite')}}</td>
<td>{{Spec2('ES6')}}</td>
<td> </td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-isfinite-number', 'isFinite')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性" style="margin-bottom: 20px; line-height: 30px;">浏览器兼容性</h2>
<p>{{Compat("javascript.builtins.isFinite")}}</p>
<h2 id="See_Also" name="See_Also" style="margin-bottom: 20px; line-height: 30px;">相关链接</h2>
<ul>
<li>{{jsxref("Number.isFinite()")}}</li>
<li>{{jsxref("Number.NaN()")}}</li>
<li>{{jsxref("Number.POSITIVE_INFINITY")}}</li>
<li>{{jsxref("Number.NEGATIVE_INFINITY")}}</li>
</ul>
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