files/zh-tw/web/javascript/reference/global_objects/number/isfinite/index.html


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---
title: Number.isFinite()
slug: Web/JavaScript/Reference/Global_Objects/Number/isFinite
tags:
  - JavaScript
  - Method
  - Number
  - Reference
translation_of: Web/JavaScript/Reference/Global_Objects/Number/isFinite
---
<div>{{JSRef}}</div>

<p><strong><code>Number.isFinite()</code></strong> 方法會判斷傳入的值是否為有限數（finite number）。</p>

<div>{{EmbedInteractiveExample("pages/js/number-isfinite.html")}}</div>


<h2 id="語法">語法</h2>

<pre class="syntaxbox">Number.isFinite(v<var>alue</var>)</pre>

<h3 id="參數">參數</h3>

<dl>
 <dt><code>value</code></dt>
 <dd>The value to be tested for finiteness.</dd>
</dl>

<h3 id="回傳值">回傳值</h3>

<p>A {{jsxref("Boolean")}} indicating whether or not the given value is a finite number.</p>

<h2 id="說明">說明</h2>

<p>In comparison to the global {{jsxref("isFinite", "isFinite()")}} function, this method doesn't forcibly convert the parameter to a number. This means only values of the type number, that are also finite, return <code>true</code>.</p>

<h2 id="範例">範例</h2>

<pre class="brush: js">Number.isFinite(Infinity);  // false
Number.isFinite(NaN);       // false
Number.isFinite(-Infinity); // false

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

Number.isFinite('0');       // false, would've been true with
                            // global isFinite('0')
Number.isFinite(null);      // false, would've been true with
                            // global isFinite(null)
</pre>

<h2 id="Polyfill">Polyfill</h2>

<pre class="brush: js">Number.isFinite = Number.isFinite || function(value) {
    return typeof value === 'number' &amp;&amp; isFinite(value);
}
</pre>

<h2 id="規範">規範</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('ES6', '#sec-number.isfinite', 'Number.isInteger')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-number.isfinite', 'Number.isInteger')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>

<p class="hidden">The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</p>

<p>{{Compat("javascript.builtins.Number.isFinite")}}</p>

<h2 id="參見">參見</h2>

<ul>
 <li>The {{jsxref("Number")}} object it belongs to.</li>
 <li>The global function {{jsxref("isFinite")}}.</li>
</ul>