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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
commit | 33058f2b292b3a581333bdfb21b8f671898c5060 (patch) | |
tree | 51c3e392513ec574331b2d3f85c394445ea803c6 /files/zh-cn/web/javascript/reference/operators/class/index.html | |
parent | 8b66d724f7caf0157093fb09cfec8fbd0c6ad50a (diff) | |
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diff --git a/files/zh-cn/web/javascript/reference/operators/class/index.html b/files/zh-cn/web/javascript/reference/operators/class/index.html new file mode 100644 index 0000000000..739c651513 --- /dev/null +++ b/files/zh-cn/web/javascript/reference/operators/class/index.html @@ -0,0 +1,112 @@ +--- +title: 类表达式 +slug: Web/JavaScript/Reference/Operators/class +tags: + - Class + - Classes + - ES6 +translation_of: Web/JavaScript/Reference/Operators/class +--- +<div>{{jsSidebar("Operators")}}</div> + +<p><strong>类表达式</strong>是用来定义类的一种语法。和<a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/function">函数表达式</a>相同的一点是,类表达式可以是命名也可以是匿名的。如果是命名类表达式,这个名字只能在类体内部才能访问到。JavaScript 的类也是基于原型继承的。</p> + +<h2 id="语法">语法</h2> + +<pre class="syntaxbox">const MyClass = class <em>[className]</em> [extends] { + // class body +};</pre> + +<h2 id="描述">描述</h2> + +<p>类表达式的语法和<a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/class">类语句</a>的语法很类似,只是在类表达式中,你可以省略掉类名,而类语句中不能。</p> + +<p>和类声明一样,类表达式中的代码也是强制<a href="/zh-CN/docs/Web/JavaScript/Reference/Strict_mode">严格模式</a>的。</p> + +<h2 id="示例">示例</h2> + +<h3 id="使用类表达式">使用类表达式</h3> + +<p>下面的代码使用类表达式语法创建了一个匿名类,然后赋值给变量 Foo。</p> + +<pre class="brush: js">let Foo = class { + constructor() {} + bar() { + return "Hello World!"; + } +}; + +let instance = new Foo(); +instance.bar(); +// "Hello World!" +</pre> + +<h3 id="命名类表达式">命名类表达式</h3> + +<p>如果你想在类体内部也能引用这个类本身,那么你就可以使用命名类表达式,并且这个类名只能在类体内部访问。</p> + +<pre class="brush: js">const Foo = class NamedFoo { + constructor() {} + whoIsThere() { + return NamedFoo.name; + } +} + +let bar = new Foo(); + +bar.whoIsThere(); +// "NamedFoo" + +NamedFoo.name; +// ReferenceError: NamedFoo is not defined + +Foo.name; +// "NamedFoo" + +</pre> + +<h2 id="规范">规范</h2> + +<table> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('ES2015', '#sec-class-definitions', 'Class definitions')}}</td> + <td>{{Spec2('ES2015')}}</td> + <td>Initial definition.</td> + </tr> + <tr> + <td>{{SpecName('ES2016', '#sec-class-definitions', 'Class definitions')}}</td> + <td>{{Spec2('ES2016')}}</td> + <td></td> + </tr> + <tr> + <td>{{SpecName('ES2017', '#sec-class-definitions', 'Class definitions')}}</td> + <td>{{Spec2('ES2017')}}</td> + <td></td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-class-definitions', 'Class definitions')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td></td> + </tr> + </tbody> +</table> + +<h2 id="浏览器兼容性">浏览器兼容性</h2> + + + +<p>{{Compat("javascript.operators.class")}}</p> + +<h2 id="相关链接">相关链接</h2> + +<ul> + <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/function"><code>函数表达式</code></a></li> + <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/class"><code>类语句</code></a></li> + <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Classes">类</a></li> +</ul> |