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The static
keyword defines a static method for a class. Static methods aren't called on instances of the class. Instead, they're called on the class itself. These are often utility functions, such as functions to create or clone objects.
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
Syntax
static methodName() { ... }
Description
Static method calls are made directly on the class and are not callable on instances of the class. Static methods are often used to create utility functions.
Calling static methods
From another static method
In order to call a static method within another static method of the same class, you can use the this
keyword.
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'
From class constructor and other methods
Static methods are not directly accessible using the this
keyword from non-static methods. You need to call them using the class name: CLASSNAME.STATIC_METHOD_NAME()
or by calling the method as a property of the constructor
: 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.'; } }
Examples
The following example demonstrates several things:
- How a static method is implemented on a class.
- That a class with a static member can be sub-classed.
- How a static method can and cannot be called.
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'.
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Class definitions' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'Class definitions' in that specification. |
Draft |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic support | 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 ? | Chrome Android Full support Yes | Edge Mobile Full support 13 | 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.