---
title: 剩余参数
slug: Web/JavaScript/Reference/Functions/Rest_parameters
tags:
  - Functions
  - JavaScript
  - Rest
  - Rest parameters
translation_of: Web/JavaScript/Reference/Functions/rest_parameters
---
<div>{{jsSidebar("Functions")}}</div>

<p><strong>剩余参数</strong>语法允许我们将一个不定数量的参数表示为一个数组。</p>

<div>{{EmbedInteractiveExample("pages/js/functions-restparameters.html")}}</div>



<h2 id="语法">语法</h2>

<pre class="brush: js">function(a, b, ...theArgs) {
  // ...
}
</pre>

<h2 id="描述">描述</h2>

<p>如果函数的最后一个命名参数以<code>...</code>为前缀，则它将成为一个由剩余参数组成的真数组，其中从<code>0</code>（包括）到<code>theArgs.length</code>（排除）的元素由传递给函数的实际参数提供。</p>

<p>在上面的例子中，<code>theArgs</code>将收集该函数的第三个参数（因为第一个参数被映射到<code>a</code>，而第二个参数映射到<code>b</code>）和所有后续参数。</p>

<h3 id="剩余参数和_arguments对象的区别">剩余参数和 <code>arguments</code>对象的区别</h3>

<p>剩余参数和 <code><a href="/zh-cn/JavaScript/Reference/Functions_and_function_scope/arguments" title="arguments">arguments</a></code>对象之间的区别主要有三个：</p>

<ul>
 <li>剩余参数只包含那些没有对应形参的实参，而 <code>arguments</code> 对象包含了传给函数的所有实参。</li>
 <li><code>arguments</code>对象不是一个真正的数组，而剩余参数是真正的 <code><a href="/zh-cn/JavaScript/Reference/Global_Objects/Array" title="Array">Array</a></code>实例，也就是说你能够在它上面直接使用所有的数组方法，比如 <code><a href="/zh-cn/JavaScript/Reference/Global_Objects/Array/sort" title="Array sort method">sort</a></code>，<code><a href="/zh-cn/JavaScript/Reference/Global_Objects/Array/map" title="Array map method">map</a></code>，<code><a href="/zh-cn/JavaScript/Reference/Global_Objects/Array/forEach" title="Array forEach method">forEach</a></code>或<code><a href="/zh-cn/JavaScript/Reference/Global_Objects/Array/pop" title="Array pop method">pop</a></code>。</li>
 <li><code>arguments</code>对象还有一些附加的属性 （如<code>callee</code>属性）。</li>
</ul>

<h3 id="从_arguments_到数组">从 arguments 到数组</h3>

<p>引入了剩余参数来减少由参数引起的样板代码。</p>

<pre><code>// Before rest parameters, "arguments" could be converted to a normal array using:

function f(a, b) {

  var normalArray = Array.prototype.slice.call(arguments);
  // -- or --
  var normalArray = [].slice.call(arguments);
  // -- or --
  var normalArray = Array.from(arguments);

  var first = normalArray.shift(); // OK, gives the first argument
  var first = arguments.shift(); // ERROR (arguments is not a normal array)

}

// Now we can easily gain access to a normal array using a rest parameter

function f(...args) {
  var normalArray = args;
  var first = normalArray.shift(); // OK, gives the first argument
}</code></pre>

<h3 id="解构剩余参数">解构剩余参数</h3>

<p>剩余参数可以被解构，这意味着他们的数据可以被解包到不同的变量中。请参阅<a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">解构赋值</a>。</p>

<pre class="brush: js">function f(...[a, b, c]) {
  return a + b + c;
}

f(1)          // NaN (b and c are undefined)
f(1, 2, 3)    // 6
f(1, 2, 3, 4) // 6 (the fourth parameter is not destructured)</pre>

<h2 id="Example">示例</h2>

<p>因为<code>theArgs</code>是个数组，所以你可以使用<code>length</code>属性得到剩余参数的个数：</p>

<pre class="brush: js">function fun1(...theArgs) {
  alert(theArgs.length);
}

fun1();  // 弹出 "0", 因为theArgs没有元素
fun1(5); // 弹出 "1", 因为theArgs只有一个元素
fun1(5, 6, 7); // 弹出 "3", 因为theArgs有三个元素</pre>

<p>下例中，剩余参数包含了从第二个到最后的所有实参，然后用第一个实参依次乘以它们：</p>

<pre class="brush: js">function multiply(multiplier, ...theArgs) {
  return theArgs.map(function (element) {
    return multiplier * element;
  });
}

var arr = multiply(2, 1, 2, 3);
console.log(arr);  // [2, 4, 6]
</pre>

<p>下例演示了你可以在剩余参数上使用任意的数组方法，而<code>arguments</code>对象不可以：</p>

<pre class="brush: js">function sortRestArgs(...theArgs) {
  var sortedArgs = theArgs.sort();
  return sortedArgs;
}

alert(sortRestArgs(5,3,7,1)); // 弹出 1,3,5,7

function sortArguments() {
  var sortedArgs = arguments.sort();
  return sortedArgs; // 不会执行到这里
}

alert(sortArguments(5,3,7,1)); // 抛出TypeError异常:arguments.sort is not a function
</pre>

<p>为了在<code>arguments</code>对象上使用<code>Array</code>方法，它必须首先被转换为一个真正的数组。</p>

<pre class="brush: js">function sortArguments() {
  var args = Array.prototype.slice.call(arguments);
  var sortedArgs = args.sort();
  return sortedArgs;
}
console.log(sortArguments(5, 3, 7, 1)); // shows 1, 3, 5, 7</pre>

<h2 id="Specifications">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-function-definitions', 'Function Definitions')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-function-definitions', 'Function Definitions')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容">浏览器兼容</h2>

<p>{{Compat("javascript.functions.rest_parameters")}}</p>

<h2 id="See_also">相关链接</h2>

<ul>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator" title="spread operator">Spread operator</a> (also ‘<code>...</code>’)</li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments" title="arguments">Arguments object</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" title="Array">Array</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions" title="Functions and function scope">Functions</a></li>
 <li><a href="http://wiki.ecmascript.org/doku.php?id=harmony:rest_parameters">Original proposal at ecmascript.org</a></li>
 <li><a href="http://javascriptweblog.wordpress.com/2011/01/18/javascripts-arguments-object-and-beyond/">JavaScript arguments object and beyond</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">Destructuring assignment</a></li>
</ul>