1. for-in
对于 string, object, array 类型使用 for-in
const str = "qwe"; const arr = ["yqcoder", "db"]; const obj = { name: "yqcoder", age: 18, }; for (let i in str) { console.log(i); // 0 1 2 } for (let i in arr) { console.log(i); // 0 1 } for (let i in obj) { console.log(i); // name age }
2. for-of
对于 string, object, array 类型使用 for-of
const str = "qwe"; const arr = ["yqcoder", "db"]; const obj = { name: "yqcoder", age: 18, }; for (let i of str) { console.log(i); // q w e } for (let i of arr) { console.log(i); // yqcoder db } for (let i of obj) { console.log(i); // obj is not iterable }
综上：for-in 可遍历 string，object，array 类型，遍历的是下标或 key，for-of 只能遍历 string, array 类型，遍历的是 value 值。
