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---
title: Number.prototype.toFixed()
slug: Web/JavaScript/Reference/Global_Objects/Number/toFixed
tags:
- JavaScript
- Method
- Number
- Prototype
translation_of: Web/JavaScript/Reference/Global_Objects/Number/toFixed
---
<div>{{JSRef}}</div>
<p><strong><code>toFixed()</code></strong> 方法會使用定點小數表示法（fixed-point notation）來格式化數字。</p>
<div>{{EmbedInteractiveExample("pages/js/number-tofixed.html")}}</div>
<h2 id="語法">語法</h2>
<pre class="syntaxbox notranslate"><code><var>numObj</var>.toFixed([<var>digits</var>])</code></pre>
<h3 id="參數">參數</h3>
<dl>
<dt><code>digits 小數位</code></dt>
<dd>選擇性輸入。顯示數值至多少個小數點，範圍由0到20之間，執行時或可支援非常大範圍的數值。如果無輸入會默認做0。</dd>
</dl>
<h3 id="回傳值">回傳值</h3>
<p>一個代表以定點小數表示法（fixed-point notation）格式化數字後的字串。</p>
<h3 id="例外">例外</h3>
<dl>
<dt>{{jsxref("RangeError")}}</dt>
<dd>If <code>digits</code> is too small or too large. Values between 0 and 100, inclusive, will not cause a {{jsxref("RangeError")}}. Implementations are allowed to support larger and smaller values as chosen.</dd>
<dt>{{jsxref("TypeError")}}</dt>
<dd>If this method is invoked on an object that is not a {{jsxref( "Number")}}.</dd>
</dl>
<h2 id="說明">說明</h2>
<p><strong><code>toFixed()</code></strong> returns a string representation of <code>numObj</code> that does not use exponential notation and has exactly <code>digits</code> digits after the decimal place. The number is rounded if necessary, and the fractional part is padded with zeros if necessary so that it has the specified length. If <code>numObj</code> is greater than <code>1e+21</code>, this method simply calls {{jsxref("Number.prototype.toString()")}} and returns a string in exponential notation.</p>
<h2 id="範例">範例</h2>
<h3 id="Using_toFixed">Using <code>toFixed</code></h3>
<pre class="brush: js notranslate">var numObj = 12345.6789;
numObj.toFixed(); // Returns '12346': note rounding, no fractional part
numObj.toFixed(1); // Returns '12345.7': note rounding
numObj.toFixed(6); // Returns '12345.678900': note added zeros
(1.23e+20).toFixed(2); // Returns '123000000000000000000.00'
(1.23e-10).toFixed(2); // Returns '0.00'
2.34.toFixed(1); // Returns '2.3'
2.35.toFixed(1); // Returns '2.4'. Note that it rounds up in this case.
-2.34.toFixed(1); // Returns -2.3 (due to operator precedence, negative number literals don't return a string...)
(-2.34).toFixed(1); // Returns '-2.3' (...unless you use parentheses)
</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('ES3')}}</td>
<td>{{Spec2('ES3')}}</td>
<td>Initial definition. Implemented in JavaScript 1.5.</td>
</tr>
<tr>
<td>{{SpecName('ES5.1', '#sec-15.7.4.5', 'Number.prototype.toFixed')}}</td>
<td>{{Spec2('ES5.1')}}</td>
<td></td>
</tr>
<tr>
<td>{{SpecName('ES6', '#sec-number.prototype.tofixed', 'Number.prototype.toFixed')}}</td>
<td>{{Spec2('ES6')}}</td>
<td></td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-number.prototype.tofixed', 'Number.prototype.toFixed')}}</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>{{Compat("javascript.builtins.Number.toFixed")}}</p>
<h2 id="參見">參見</h2>
<ul>
<li>{{jsxref("Number.prototype.toExponential()")}}</li>
<li>{{jsxref("Number.prototype.toPrecision()")}}</li>
<li>{{jsxref("Number.prototype.toString()")}}</li>
</ul>
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