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+---
+title: setter
+slug: Web/JavaScript/Reference/Functions/set
+tags:
+  - ECMAScript 5
+  - Functions
+  - JavaScript
+translation_of: Web/JavaScript/Reference/Functions/set
+---
+<div>{{jsSidebar("Functions")}}</div>
+
+<p>当尝试设置属性时，<strong><code>set</code></strong>语法将对象属性绑定到要调用的函数。</p>
+
+<div>{{EmbedInteractiveExample("pages/js/functions-setter.html")}}</div>
+
+
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox">{set <em>prop</em>(<em>val</em>) { . . . }}
+{set [expression](<em>val</em>) { . . . }}</pre>
+
+<h3 id="参数">参数</h3>
+
+<dl>
+ <dt><code>prop</code></dt>
+ <dd>要绑定到给定函数的属性名。</dd>
+</dl>
+
+<dl>
+ <dt><code>val</code></dt>
+ <dd>用于保存尝试分配给<code>prop</code>的值的变量的一个别名。</dd>
+ <dt>表达式</dt>
+ <dd>从 ECMAScript 2015 开始，还可以使用一个计算属性名的表达式绑定到给定的函数。</dd>
+</dl>
+
+<h2 id="描述">描述</h2>
+
+<p>在 javascript 中，如果试着改变一个属性的值，那么对应的 setter 将被执行。setter 经常和 getter 连用以创建一个伪属性。不可能在具有真实值的属性上同时拥有一个 setter 器。</p>
+
+<p>使用 set 语法时请注意：</p>
+
+<div>
+<ul>
+ <li>它的标识符可以是数字或字符串；</li>
+ <li>它必须有一个明确的参数 （详见 <a class="external" href="http://whereswalden.com/2010/08/22/incompatible-es5-change-literal-getter-and-setter-functions-must-now-have-exactly-zero-or-one-arguments/" rel="external nofollow">Incompatible <abbr title="ECMAScript 5th edition">ES5</abbr> change: literal getter and setter functions must now have exactly zero or one arguments</a>）；</li>
+ <li>在对象字面量中，不能为一个已有真实值的变量使用 set ，也不能为一个属性设置多个 set。<br>
+  ( <code>{ set x(v) { }, set x(v) { } }</code> 和 <code>{ x: ..., set x(v) { } }</code> 是不允许的 )</li>
+</ul>
+</div>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="Example_Defining_a_getter_with_the_get_operator" name="Example:_Defining_a_getter_with_the_get_operator">在对象初始化时定义 setter</h3>
+
+<p>这将定义一个对象 <code><font face="consolas, Liberation Mono, courier, monospace">language</font></code> 的伪属性<code>current</code>，当<code>current</code>被分配一个值时，将使用该值更新<code>log</code>：</p>
+
+<pre class="brush: js">const language = {
+  set current(name) {
+    this.log.push(name);
+  },
+  log: []
+}
+
+language.current = 'EN';
+console.log(language.log); // ['EN']
+
+language.current = 'FA';
+console.log(language.log); // ['EN', 'FA']</pre>
+
+<p>请注意，<code>current</code>属性是未定义的，访问它时将会返回 <code>undefined</code>。</p>
+
+<h3 id="Example_Removing_a_setter_with_the_delete_operator" name="Example:_Removing_a_setter_with_the_delete_operator">用 <code>delete</code> 操作符移除一个 setter</h3>
+
+<p>我们可以使用<code><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete">delete</a></code>操作符移除 setter。</p>
+
+<pre class="brush: js">delete language.current;
+</pre>
+
+<h3 id="使用_defineProperty_为当前对象定义_setter">使用 <code>defineProperty</code> 为当前对象定义 setter</h3>
+
+<p>我们可以随时使用 {{jsxref("Object.defineProperty()")}} 给一个已经存在的对象添加一个 setter。</p>
+
+<pre class="brush: js">const o = { a:0 };
+
+Object.defineProperty(o, "b", { set: function (x) { this.a = x / 2; } });
+
+o.b = 10; // Runs the setter, which assigns 10 / 2 (5) to the 'a' property
+console.log(o.a) // 5</pre>
+
+<h3 id="使用计算属性名">使用计算属性名</h3>
+
+<pre class="brush: js">const expr = "foo";
+
+const obj = {
+  baz: "bar",
+  set [expr](v) { this.baz = v; }
+};
+
+console.log(obj.baz); // "bar"
+obj.foo = "baz";      // run the setter
+console.log(obj.baz); // "baz"
+</pre>
+
+<h2 id="规范"><span class="def"><span>规范</span></span></h2>
+
+<table class="standard-table">
+ <thead>
+  <tr>
+   <th scope="col">Specification</th>
+  </tr>
+ </thead>
+ <tbody>
+  <tr>
+   <td>{{SpecName('ESDraft', '#sec-method-definitions', 'Method definitions')}}</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容">浏览器兼容</h2>
+
+<div class="hidden">The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
+
+<p>{{Compat("javascript.functions.set")}}</p>
+
+<h2 id="See_also" name="See_also">相关链接</h2>
+
+<ul>
+ <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Functions/get">getter</a></li>
+ <li>{{jsxref("Operators/delete", "delete")}}</li>
+ <li>{{jsxref("Object.defineProperty()")}}</li>
+ <li>{{jsxref("Object.defineGetter", "__defineGetter__")}}</li>
+ <li>{{jsxref("Object.defineSetter", "__defineSetter__")}}</li>
+ <li><a href="/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters">Defining Getters and Setters</a> in JavaScript Guide</li>
+</ul>