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---
title: Math.log1p()
slug: Web/JavaScript/Reference/Global_Objects/Math/log1p
translation_of: Web/JavaScript/Reference/Global_Objects/Math/log1p
---
<div>
<div>{{JSRef("Global_Objects", "Math")}}</div>
</div>
<h2 id="Summary" name="Summary">概述</h2>
<p><code><strong>Math.log1p()</strong></code> 函数返回一个数字加1后的自然对数 (底为 <code>E</code>), 既<code>log(x+1)</code>.</p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre class="syntaxbox"><code>Math.log1p(<em>x</em>)</code></pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>x</code></dt>
<dd>任意数字.</dd>
</dl>
<h2 id="Description" name="Description">描述</h2>
<p>如果参数的值小于<code> -1</code>, 则返回 <code>NaN.</code></p>
<p><code>函数 y = log(x+1) 的图形是这样的:</code></p>
<p> <img alt="log(x+1)" src="https://mdn.mozillademos.org/files/6467/logx1.jpg"></p>
<p><strong>示例</strong></p>
<pre class="brush:js">Math.log1p(Math.E-1) // 1
Math.log1p(0) // 0
Math.log1p("0") // 0
Math.log1p(-1) // -Infinity
Math.log1p(-2) // NaN
Math.log1p("foo") // NaN
</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>{{SpecName('ES6', '#sec-math.log1p', 'Math.log1p')}}</td>
<td>{{Spec2('ES6')}}</td>
<td>Initial definition.</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{ CompatibilityTable() }}</p>
<div>
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td>{{CompatNo}}</td>
<td>{{CompatGeckoDesktop("25")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
</tr>
</tbody>
</table>
</div>
<div>
<table class="compat-table">
<tbody>
<tr>
<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>
</tr>
<tr>
<td>Basic support</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatGeckoMobile("25")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
</tr>
</tbody>
</table>
</div>
<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li>{{jsxref("Global_Objects/Math", "Math")}} 对象.</li>
</ul>
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