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---
title: 'RangeError: precision is out of range'
slug: Web/JavaScript/Reference/Errors/Precision_range
tags:
- JavaScript
- 范围错误
- 错误
translation_of: Web/JavaScript/Reference/Errors/Precision_range
---
<div>{{jsSidebar("Errors")}}</div>
<h2 id="描述">描述</h2>
<pre class="syntaxbox">RangeError: precision {0} out of range (Firefox)
RangeError: toExponential() argument must be between 0 and 20 (Chrome)
RangeError: toFixed() digits argument must be between 0 and 20 (Chrome)
RangeError: toPrecision() argument must be between 1 and 21 (Chrome)
</pre>
<h2 id="错误类型">错误类型</h2>
<p>{{jsxref("RangeError")}}</p>
<h2 id="什么地方出错了？">什么地方出错了？</h2>
<p>以下的某个方法传入了一个超出精度范围的参数：</p>
<ul>
<li>{{jsxref("Number.prototype.toExponential()")}}</li>
<li>{{jsxref("Number.prototype.toFixed()")}}</li>
<li>{{jsxref("Number.prototype.toPrecision()")}}</li>
</ul>
<p>通常这些方法允许的参数范围介于0和20（或21）之间。需要注意的是，ECMAScript标准是允许扩展这个范围的。</p>
<table class="standard-table">
<thead>
<tr>
<th scope="col">Method</th>
<th scope="col">Firefox (SpiderMonkey)</th>
<th scope="col">Chrome, Opera (V8)</th>
</tr>
</thead>
<tbody>
<tr>
<td>{{jsxref("Number.prototype.toExponential()")}}</td>
<td>0 to 100</td>
<td>0 to 20</td>
</tr>
<tr>
<td>{{jsxref("Number.prototype.toFixed()")}}</td>
<td>-20 to 100</td>
<td>0 to 20</td>
</tr>
<tr>
<td>{{jsxref("Number.prototype.toPrecision()")}}</td>
<td>1 to 100</td>
<td>1 to 21</td>
</tr>
</tbody>
</table>
<h2 id="示例">示例</h2>
<h3 id="错误的示例">错误的示例</h3>
<pre class="brush: js example-bad">77.1234.toExponential(-1); // RangeError
77.1234.toExponential(101); // RangeError
2.34.toFixed(-100); // RangeError
2.34.toFixed(1001); // RangeError
1234.5.toPrecision(-1); // RangeError
1234.5.toPrecision(101); // RangeError
</pre>
<h3 id="正确的示例">正确的示例</h3>
<pre class="brush: js example-good">77.1234.toExponential(4); // 7.7123e+1
77.1234.toExponential(2); // 7.71e+1
2.34.toFixed(1); // 2.3
2.35.toFixed(1); // 2.4 (note that it rounds up in this case)
5.123456.toPrecision(5); // 5.1235
5.123456.toPrecision(2); // 5.1
5.123456.toPrecision(1); // 5
</pre>
<h2 id="相关页面">相关页面</h2>
<ul>
<li>{{jsxref("Number.prototype.toExponential()")}}</li>
<li>{{jsxref("Number.prototype.toFixed()")}}</li>
<li>{{jsxref("Number.prototype.toPrecision()")}}</li>
</ul>
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