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---
title: Number.POSITIVE_INFINITY
slug: Web/JavaScript/Reference/Global_Objects/Number/POSITIVE_INFINITY
translation_of: Web/JavaScript/Reference/Global_Objects/Number/POSITIVE_INFINITY
---
<div>{{JSRef("Global_Objects", "Number")}}</div>
<h2 id="概述">概述</h2>
<p><code><strong>Number.POSITIVE_INFINITY</strong></code> 属性表示正无穷大。</p>
<p>不必创建一个 {{jsxref("Global_Objects/Number", "Number")}} 实例，可使用 <code>Number.POSITIVE_INFINITY</code> 来访问该静态属性。</p>
<p>{{js_property_attributes(0,0,0)}}</p>
<h2 id="描述">描述</h2>
<p><code>Number.POSITIVE_INFINITY</code> 的值同全局对象 {{jsxref("Global_Objects/Infinity", "Infinity")}} 属性的值相同。</p>
<p>该值的表现同数学上的无穷大有点儿不同：</p>
<ul>
<li>任何正值，包括 <code>POSITIVE_INFINITY</code>，乘以 <code>POSITIVE_INFINITY</code> 为 <code>POSITIVE_INFINITY</code>。</li>
<li>任何负值，包括 <code>NEGATIVE_INFINITY</code>，乘以 <code>POSITIVE_INFINITY</code> 为 <code>NEGATIVE_INFINITY</code>。</li>
<li>0 乘以 <code>POSITIVE_INFINITY</code> 为 NaN。</li>
<li>NaN 乘以 <code>POSITIVE_INFINITY</code> 为 NaN。</li>
<li><code>POSITIVE_INFINITY</code> 除以 <code>NEGATIVE_INFINITY</code> 以外的任何负值为 <code>NEGATIVE_INFINITY</code>。</li>
<li><code>POSITIVE_INFINITY</code> 除以 <code>POSITIVE_INFINITY</code> 以外的任何正值为 <code>POSITIVE_INFINITY</code>。</li>
<li><code>POSITIVE_INFINITY</code> 除以 <code>NEGATIVE_INFINITY</code> 或 <code>POSITIVE_INFINITY</code> 为 NaN。</li>
<li>任何数除以 <code>POSITIVE_INFINITY</code> 为 0。</li>
</ul>
<p>You might use the <code>Number.POSITIVE_INFINITY</code> property to indicate an error condition that returns a finite number in case of success. Note, however, that {{jsxref("Global_Objects/isFinite", "isFinite")}} would be more appropriate in such a case.</p>
<h2 id="示例">示例</h2>
<p>下例中，赋值给变量 <code>bigNumber</code> 一个大于 JavaScript 中最大值的值。当 <code>if</code> 语句执行时，变量 <code>bigNumber</code> 值为 "<code>Infinity</code>"， 因此在继续执行代码前，为变量 <code>bigNumber</code> 设置一个容易管理的值。</p>
<pre class="brush: js">var bigNumber = Number.MAX_VALUE * 2
if (bigNumber == Number.POSITIVE_INFINITY) {
bigNumber = returnFinite();
}
</pre>
<h2 id="规范">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>ECMAScript 1st Edition. Implemented in JavaScript 1.1</td>
<td>Standard</td>
<td>Initial definition.</td>
</tr>
<tr>
<td>{{SpecName('ES5.1', '#sec-15.7.3.6', 'Number.POSITIVE_INFINITY')}}</td>
<td>{{Spec2('ES5.1')}}</td>
<td> </td>
</tr>
<tr>
<td>{{SpecName('ES6', '#sec-number.positive_infinity', 'Number.POSITIVE_INFINITY')}}</td>
<td>{{Spec2('ES6')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
{{Compat}}
<h2 id="See_also">相关链接</h2>
<ul>
<li>{{jsxref("Number.NEGATIVE_INFINITY")}}</li>
<li>{{jsxref("Global_Objects/Infinity", "Infinity")}}</li>
<li>{{jsxref("Global_Objects/isFinite", "isFinite")}}</li>
</ul>
|
