Map.prototype[Symbol.iterator]()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Map 实例的 [Symbol.iterator]() 方法实现了 可迭代协议 并允许大多数需要迭代的语法使用 Map 对象，例如 扩展语法 和 for...of 循环。它返回一个 映射迭代器对象，它按插入顺序生成映射的键值对。
¥The [Symbol.iterator]() method of Map instances implements the iterable protocol and allows Map objects to be consumed by most syntaxes expecting iterables, such as the spread syntax and for...of loops. It returns a map iterator object that yields the key-value pairs of the map in insertion order.
该属性的初始值与 Map.prototype.entries 属性的初始值是相同的函数对象。
¥The initial value of this property is the same function object as the initial value of the Map.prototype.entries property.
Try it
语法
参数
返回值
¥Return value
与 Map.prototype.entries() 返回值相同：一个新的 可迭代的迭代器对象，它生成映射的键值对。
¥The same return value as Map.prototype.entries(): a new iterable iterator object that yields the key-value pairs of the map.
示例
使用 for...of 循环进行迭代
¥Iteration using for...of loop
请注意，你很少需要直接调用此方法。[Symbol.iterator]() 方法的存在使得 Map 对象成为 iterable，像 for...of 循环这样的迭代语法会自动调用该方法来获取要循环的迭代器。
¥Note that you seldom need to call this method directly. The existence of the [Symbol.iterator]() method makes Map objects iterable, and iterating syntaxes like the for...of loop automatically call this method to obtain the iterator to loop over.
const myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");
for (const entry of myMap) {
console.log(entry);
}
// ["0", "foo"]
// [1, "bar"]
// [{}, "baz"]
for (const [key, value] of myMap) {
console.log(`${key}: ${value}`);
}
// 0: foo
// 1: bar
// [Object]: baz
手动滚动迭代器
¥Manually hand-rolling the iterator
你仍然可以手动调用返回的迭代器对象的 next() 方法，以实现对迭代过程的最大控制。
¥You may still manually call the next() method of the returned iterator object to achieve maximum control over the iteration process.
const myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");
const mapIter = myMap[Symbol.iterator]();
console.log(mapIter.next().value); // ["0", "foo"]
console.log(mapIter.next().value); // [1, "bar"]
console.log(mapIter.next().value); // [Object, "baz"]
规范
| Specification |
|---|
| ECMAScript Language Specification # sec-map.prototype-@@iterator |
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