方法定義

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This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

自 ECMAScript 2015 開始，引入了一種於物件初始器（objects initializers）中定義方法的簡短語法。是一個將函式指派予方法名稱的簡便方式。

嘗試一下

const obj = { foo() { return "bar"; }, }; console.log(obj.foo()); // Expected output: "bar"

語法

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) {} };

說明

這個簡短的語法和在 ECMAScript 2015 引入 getter 以及 setter 類似。

請看以下程式碼：

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

你可以把它縮減為：

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

產生器方法

產生器方法（Generator method）也可以透過簡短語法定義之。用的時候：

簡短語法的星號（*）必須放在產生器方法的屬性名前面。也就是說 * g(){} 能動但 g *(){} 不行；
非產生器方法的定義可能不會有 yield 關鍵字。也就是說過往的產生器函式動不了、並拋出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 方法

Async 方法也可以透過簡短語法定義。

// 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)

範例

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

規範

Specification
ECMAScript® 2026 Language Specification # sec-method-definitions