类(class)通过 static 关键字定义静态方法。不能在类的实例上调用静态方法,而应该通过类本身调用。这些通常是实用程序方法,例如创建或克隆对象的功能。
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语法
static methodName() { ... }
描述
静态方法调用直接在类上进行,不能在类的实例上调用。静态方法通常用于创建实用程序函数。
调用静态方法
从另一个静态方法
静态方法调用同一个类中的其他静态方法,可使用 this
关键字。
class StaticMethodCall { static staticMethod() { return 'Static method has been called'; } static anotherStaticMethod() { return this.staticMethod() + ' from another static method'; } } StaticMethodCall.staticMethod(); // 'Static method has been called' StaticMethodCall.anotherStaticMethod(); // 'Static method has been called from another static method'
从类的构造函数和其他方法
非静态方法中,不能直接使用 this
关键字来访问静态方法。而是要用类名来调用:CLASSNAME.STATIC_METHOD_NAME()
,或者用构造函数的属性来调用该方法: this.constructor.STATIC_METHOD_NAME()
.
class StaticMethodCall { constructor() { console.log(StaticMethodCall.staticMethod()); // 'static method has been called.' console.log(this.constructor.staticMethod()); // 'static method has been called.' } static staticMethod() { return 'static method has been called.'; } }
示例
下面的例子说明了这几点:
- 静态方法如何在类上实现。
- 具有静态成员的类,可以被子类化 。
- 什么情况下静态方法可以调用,什么情况下不能调用。
class Tripple { static tripple(n = 1) { return n * 3; } } class BiggerTripple extends Tripple { static tripple(n) { return super.tripple(n) * super.tripple(n); } } console.log(Tripple.tripple());// 3 console.log(Tripple.tripple(6));// 18 let tp = new Tripple(); console.log(BiggerTripple.tripple(3));// 81(不会受父类实例化的影响) console.log(tp.tripple());// 'tp.tripple 不是一个函数'.
规范
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) Class definitions |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) Class definitions |
Draft |
浏览器兼容
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out
https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
static |
Chrome Full support 49
|
Edge Full support 13 | Firefox Full support 45 | IE No support No | Opera Full support 36 | Safari Full support 9 | WebView Android Full support 49
|
Chrome Android Full support 49
|
Firefox Android Full support 45 | Opera Android ? | Safari iOS Full support 9 | Samsung Internet Android Full support Yes | nodejs Full support 6.0.0
|
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.