//将一个或者多个源对象中所有可枚举的自有属性复制到目标对象，并返回修改后的目标对象
let obj = {'a':'1','b':'2'}
let obj2 = {'c':'3','d':'4'}
let obj3 = {'e':'5','f':'6'}
console.log(Object.assign(obj,obj2)); //{ a: '1', b: '2', c: '3', d: '4' }
console.log(Object.assign(obj,obj2,obj3));//{ a: '1', b: '2', c: '3', d: '4', e: '5', f: '6' }

let obj = {'a':'1','b':'2'}
let obj2 = {'c':'3','d':'4',test:function(){
    console.log('test');
}}
Object.assign(obj,obj2).test() //test 也是可以调用的

let obj = {'a':'1','b':'2'}
console.log(Object.entries(obj)); //[ [ 'a', '1' ], [ 'b', '2' ] ]

//可以使一个对象被冻结. 不可更改 深拷贝之后的可更改
let obj = {'a':'1','b':'2'}
Object.freeze(obj)
obj.a = '3'
console.log(obj); //{'a':'1','b':'2'}

//将键值对列表转换为一个对象
let obj = [['a','1','11'],['b','2'],['c','3'],['d']]
console.log(Object.fromEntries(obj));//{ a: '1', b: '2', c: '3', d: undefined }

    let obj = [
      {
        id: 2, name: '张三', age: 38, sex: '男',
      },
      {
        id: 1, name: '李四', age: 17, sex: '女',
      },
      {
        id: 3, name: '王五', age: 28, sex: '男',
      },
    ]
    let obj2 = Object.groupBy(obj, ({ age }) => {
      return age
    })
    let obj3 = Object.values(obj2).map((item) => {
      return item[0]
    })
    console.log(obj2);
    console.log(obj3);
    console.log(Object.values(obj2));
    

console.log(obj2);

console.log(obj3);

console.log(Object.values(obj2));

//确定两个值是否为相同值
let obj = { a: '1' }
let obj2 = { a: '1' }
let obj3 = obj
console.log(Object.is(obj, obj2)); //false 为对象时 比较是否引用了内存中的同一对象
console.log(Object.is(obj, obj3)); //true
console.log(Object.is(1,1));  //true
console.log(Object.is(1,'1')); //false
console.log(Object.is(-0,0)); //false
console.log(Object.is(null,undefined)); //false

//判断一个对象是否是可扩展的

//判断一个对象是否被冻结

//判断一个对象是否被密封

//返回一key组成的数组
let obj1 = {'a':'1', 'b':'2', 'c':'3'}
console.log(Object.keys(obj1)) //[ 'a', 'b', 'c' ]

//防止新属性被添加到对象中（即防止该对象被扩展）。它还可以防止对象的原型被重新指定
//不可新增 可修改删除  
let obj1 = {'a':'1'}
Object.preventExtensions(obj1)
obj1.b = '2'
console.log(obj1) //{'a':'1'}

let obj1 = {'a':'1'}
Object.preventExtensions(obj1)
obj1.a = '2'
console.log(obj1) //{'a':'2'}

let obj1 = {'a':'1'}
Object.preventExtensions(obj1)
delete obj1.a
console.log(obj1) //{}

//返回value组成的数组
let obj1 = {'a':'1', 'b':'2', 'c':'3'}
console.log(Object.values(obj1)) //[ '1', '2', '3' ]