示例

//注意: 编译目标为ES5或ES3时,迭代器只允许在Array类型上使用
let list = [4, 5, 6];
//for..in迭代的是对象的键
for (let i in list) {
    console.log(i); // "0", "1", "2",
}
//for..of则迭代对象的键对应的值
for (let i of list) {
    console.log(i); // "4", "5", "6"
}

运行测试