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Starting with ECMAScript 2015, a shorter syntax for method definitions on objects initializers is introduced. It is a shorthand for a function assigned to the method's name.

Syntax

var obj = {
  property( parameters… ) {},
  *generator( parameters… ) {},
  async property( parameters… ) {},
  async* generator( parameters… ) {},

  // with computed keys:
  [property]( parameters… ) {},
  *[generator]( parameters… ) {},
  async [property]( parameters… ) {},

  // compare getter/setter syntax:
  get property() {},
  set property(value) {}
};

Description

The shorthand syntax is similar to the getter and setter syntax introduced in ECMAScript 2015.

Given the following code:

var obj = {
  foo: function() {
    /* code */
  },
  bar: function() {
    /* code */
  }
};

You are now able to shorten this to:

var obj = {
  foo() {
    /* code */
  },
  bar() {
    /* code */
  }
};

Generator methods

Generator methods can be defined using the shorthand syntax as well. When using them,

  • the asterisk (*) in the shorthand syntax must be before the generator property name. That is, * g(){} will work but g *(){} will not;
  • non-generator method definitions may not contain the yield keyword. This means that legacy generator functions won't work either and will throw a SyntaxError. Always use yield in conjunction with the asterisk (*).

// Using a named property
var obj2 = {
  g: function* () {
    var index = 0;
    while (true)
      yield index++;
  }
};

// The same object using shorthand syntax
var obj2 = { 
  * g() {
    var index = 0;
    while (true)
      yield index++;
  }
};

var it = obj2.g();
console.log(it.next().value); // 0
console.log(it.next().value); // 1

Async methods

Async methods can also be defined using the shorthand syntax.

// Using a named property
var obj3 = {
  f: async function () {
    await some_promise;
  }
};

// The same object using shorthand syntax
var obj3 = { 
  async f() {
    await some_promise;
  }
};

Async generator methods

Generator methods can also be async.

var obj4 = {
  f: async function* () {
    yield 1;
    yield 2;
    yield 3;
  }
};

// The same object using shorthand syntax
var obj4 = {
  async* f() {
   yield 1;
   yield 2;
   yield 3;
  }
};

Method definitions are not constructable

All method definitions are not constructors and will throw a TypeError if you try to instantiate them.

var obj = { 
  method() {}
};
new obj.method; // TypeError: obj.method is not a constructor

var obj = { 
  * g() {} 
};
new obj.g; // TypeError: obj.g is not a constructor (changed in ES2016)

Examples

Simple test case

var obj = {
  a: 'foo',
  b() { return this.a; }
};
console.log(obj.b()); // "foo"

Computed property names

The shorthand syntax also supports computed property names.

var bar = {
  foo0: function() { return 0; },
  foo1() { return 1; },
  ['foo' + 2]() { return 2; }
};

console.log(bar.foo0()); // 0
console.log(bar.foo1()); // 1
console.log(bar.foo2()); // 2

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Method definitions' in that specification.
Standard Initial definition.
ECMAScript 2016 (ECMA-262)
The definition of 'Method definitions' in that specification.
Standard Changed that generator methods should also not have a [[Construct]] trap and will throw when used with new.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Method definitions' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 39Edge Full support YesFirefox Full support 34IE No support NoOpera Full support 26Safari No support NoWebView Android Full support 39Chrome Android Full support 39Edge Mobile Full support YesFirefox Android Full support 34Opera Android Full support 26Safari iOS No support NoSamsung Internet Android Full support 4.0nodejs Full support Yes
Generator methods are not constructable (ES2016)Chrome ? Edge ? Firefox Full support 43IE No support NoOpera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 43Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs ?
Async methodsChrome ? Edge ? Firefox Full support 52IE No support NoOpera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 52Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs Full support 7.6.0
Full support 7.6.0
Full support 7.0.0
Disabled
Disabled From version 7.0.0: this feature is behind the --harmony runtime flag.
Async generator methodsChrome ? Edge ? Firefox Full support 55IE No support NoOpera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 55Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs Full support 10.0.0
Full support 10.0.0
Full support 8.10.0
Disabled
Disabled From version 8.10.0: this feature is behind the --harmony runtime flag.

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Autorzy i etykiety dokumentu

Ostatnia aktualizacja: wbamberg,