static

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Ключовата дума static дефинира статичен метод за клас. Static methods aren't called on instances of the class. Instead, they're called on the class itself. Това често са помощни функции, като например функции за създаване или клониране на обекти.

Синтаксис

static methodName() { ... }

Описание

Статичните методи се правят директно в класът и не могат да се извикват като инстанции на клас.

Извикване на статичен метод

От друг статичен метод

За да извикате статичен метод в рамките на друг статичен метод от същия клас, може да използвате ключовата дума this.

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'

От конструктора на клас и други методи

Статичните методи не са пряко достъпни, когато се използва ключовата дума this от нестатични методи. Трябва да ги извикате, използвайки името на класа: CLASSNAME.STATIC_METHOD_NAME() или да извикате метода като собственост на constructorthis.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.';
  }
}

Примери

Следният пример показва няколко неща:

  1. Как статичните методи се изпълняват в класът.
  2. Това , че клас със статичен член може да бъде под-класиран.
  3. Как статичният метод може и не може да бъде извикан.
class Triple {
  static triple(n) {
    if (n === undefined) {
      n = 1;
    }
    return n * 3;
  }
}

class BiggerTriple extends Triple {
  static triple(n) {
    return super.triple(n) * super.triple(n);
  }
}

console.log(Triple.triple());        // 3
console.log(Triple.triple(6));       // 18

var tp = new Triple();

console.log(BiggerTriple.triple(3));
// 81 (not affected by parent's instantiation)

console.log(tp.triple());
// 'tp.triple is not a function'.

Спецификации

Спецификации Статус Коментар
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Class definitions' in that specification.
Standard Initial definition.
ECMAScript (ECMA-262)
The definition of 'Class definitions' in that specification.
Living Standard  

Съвместимост с браузера

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
staticChrome Full support 49
Full support 49
No support 42 — 49
Notes
Notes Strict mode is required.
No support 42 — 49
Disabled
Disabled From version 42 until version 49 (exclusive): this feature is behind the Experimental JavaScript preference (needs to be set to Enabled). To change preferences in Chrome, visit chrome://flags.
Edge Full support 13Firefox Full support 45IE No support NoOpera Full support 36
Full support 36
No support 29 — 36
Notes
Notes Strict mode is required.
No support 29 — 36
Disabled
Disabled From version 29 until version 36 (exclusive): this feature is behind the Experimental JavaScript preference (needs to be set to Enabled).
Safari Full support 9WebView Android Full support 49
Full support 49
No support 42 — 49
Notes
Notes Strict mode is required.
Chrome Android Full support 49
Full support 49
No support 42 — 49
Notes
Notes Strict mode is required.
No support 42 — 49
Disabled
Disabled From version 42 until version 49 (exclusive): this feature is behind the Experimental JavaScript preference (needs to be set to Enabled). To change preferences in Chrome, visit chrome://flags.
Firefox Android Full support 45Opera Android Full support 36
Full support 36
No support 29 — 36
Notes
Notes Strict mode is required.
No support 29 — 36
Disabled
Disabled From version 29 until version 36 (exclusive): this feature is behind the Experimental JavaScript preference (needs to be set to Enabled).
Safari iOS Full support 9Samsung Internet Android Full support 5.0
Full support 5.0
No support 4.0 — 5.0
Notes
Notes Strict mode is required.
nodejs Full support 6.0.0
Full support 6.0.0
Full support 4.0.0
Disabled
Disabled From version 4.0.0: this feature is behind the --use_strict runtime flag.
Full support 5.0.0
Disabled
Disabled From version 5.0.0: this feature is behind the --harmony runtime flag.

Legend

Full support  
Full support
No support  
No support
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

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