js的中for in和for of

let obj = {name: '小明', age: 18}
    for (let key in obj) {
      console.log(obj[key])
    }

    let arr = [{'name': '小明', 'age': 18}, {'name': '小明', 'age': 18}]
    for (let key of arr) {
      console.log(key)
    }
let obj = {name: '小明', age: 18}
    for (let