Object.fromEntries() 静态方法将键值对列表转换为一个对象

将 Array 转换成对象：

let arr = [["name","张三"],["age","40"]]
let obj = Object.fromEntries(arr);
console.log(obj);

将 Map 转换成对象：

let map = new Map()
map.set("name","李四")
map.set("age",50)
let person = Object.fromEntries(map)
console.log(person);

对象转换:

需求：计算出键名对应的键值的长度，并返回一个新的对象

 let Obj = {"A":["a1","a2","a3"],"B":["b1","b2"],"C":["c1"],}let myarr = Object.entries(Obj).map(([key,val])=>{return [key,val.length]})let myobj = Object.fromEntries(myarr)console.log(myobj);