Map.prototype[@@iterator]()

@@iterator 属性的初始值与 entries 属性的初始值是同一个函数对象。

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myMap[Symbol.iterator]

map 的 iterator 函数默认就是 entries() 函数。

var myMap = new Map();
myMap.set('0', 'foo');
myMap.set(1, 'bar');
myMap.set({}, 'baz');

var mapIter = myMap[Symbol.iterator]();
//返回的其实是个generator
console.log(mapIter.next().value); // ["0", "foo"]
console.log(mapIter.next().value); // [1, "bar"]
console.log(mapIter.next().value); // [Object, "baz"]

var 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 (var v of myMap) {
  console.log(v);
}

// 0: foo
// 1: bar
// [Object]: baz

• Map.prototype.entries()
• Map.prototype.keys()
• Map.prototype.values()