Method definitions

In This Article

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 */
  }
};

Note : The shorthand syntax uses named function instead of anonymous functions (as in …foo: function() {}…). Named functions can be called from the function body (this is impossible for anonymous function as there is no identifier to refer to). For more details, see function.

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;
  }
};