---
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">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">语法</h2>

<pre class="syntaxbox"><code>Math.log1p(<em>x</em>)</code></pre>

<h3 id="Parameters">参数</h3>

<dl>
 <dt><code>x</code></dt>
 <dd>任意数字.</dd>
</dl>

<h2 id="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>

{{Compat}}

<h2 id="See_also">相关链接</h2>

<ul>
 <li>{{jsxref("Global_Objects/Math", "Math")}} 对象.</li>
</ul>