浅拷贝

1. Object.assign

   let obj = {a:1,b:{c:3}}
   let obj1 = Object.assign(obj)
   obj1.b.c = '哈哈'
   console.log(obj, obj1)
   

   
2. 拓展运算符

   let obj = {a:1,b:{c:3}}
   let obj1 = {...obj}
   obj1.b.c = '哈哈'
   console.log(obj, obj1)
   

3. concat（只针对数组）

   let arr = [{name:"Livia"},{name:"David"},{name:"Frank"}]
   let arr1 = arr.concat()
   arr1[2].name += "！！"
   console.log(arr, arr1)
   

   
4. slice（只针对数组）

   let arr = [{name:"Livia"},{name:"David"},{name:"Frank"}]
   let arr1 = arr.slice()
   arr1[2].name += "！！"
   console.log(arr, arr1)
   

深拷贝

1. JSON.stringify

2. 第三方库，lodash._cloneDeep()

3. 简易递归

    function myDeep(obj) {
      let res = {}
      for (let key in obj) {
          if(typeof obj[key] !== 'object' && obj[key] !== null){
              res[key] = obj[key]
          }  else {
            res[key] = myDeep(obj[key])
          }
      }
      return res
    }
    let obj = {
      a: 1,
      b: {
        c: 3,
      }
    }
   
    let obj1 = myDeep(obj)
    obj1.b.c = 666
    console.log(obj, obj1)
   

   

4. 持续完善版 上述的简易版存在以下问题：

   • 无法正确复制不可枚举属性
     • 使用Reflect.ownKeys解决
   • 只能正确复制基础数据类型，而对于Array、Function等无法正确复制
     • 当遇到Date、RegExp等实例，重新生成对应实例
   • 循环引用问题
     • weakMap作为hash表，可以解决弱引用问题（挖个坑🕳）

   制造难题

   let obj = {
     num: 0,
     str: 'haha',
     bool: true,
     unf: undefined,
     nul: null,
     obj: {
       name:"Frank"
     },
     arr: [5,6,7],
     func: function() {console.log("Hello, Frank")},
     date: new Date(0),
     reg: new RegExp('/正则/ig'),
     [Symbol('1')]: 1,
   }
   
   Object.defineProperty(obj, 'innumerable', {
     enumerable: false,
     value: '不可枚举'
   })
   
   obj.loop = obj
   
   console.log(obj)
   

   

   改良版(有bug，下次再改)

   let obj = {
     num: 0,
     str: 'haha',
     bool: true,
     unf: undefined,
     nul: null,
     obj: {
       name:"Frank"
     },
     arr: [5,6,7],
     func: function() {console.log("Hello, Frank")},
     date: new Date(0),
     reg: new RegExp('/正则/ig'),
     [Symbol('1')]: 1,
   }
   
   Object.defineProperty(obj, 'innumerable', {
     enumerable: false,
     value: '不可枚举'
   })
   
   obj.loop = obj
   
   function deepPlus(obj, map = new WeakMap()) {
     let res = {}
     if(obj instanceof RegExp){
       return new RegExp(obj)
     }
     if(obj instanceof Date){
       return new Date(obj)
     }
     if(map.has(obj)) {
       return map.get(obj)
     }
     let allDesc = Object.getOwnPropertyDescriptors(obj)
     map.set(obj, allDesc)
     for (let key of Reflect.ownKeys(obj)) {
       console.log('key', key, typeof obj[key])
         if(typeof obj[key] === 'object' && obj[key] !== null){
             res[key] = deepPlus(obj[key], map)
         }  else {
           res[key] = obj[key]
         }
     }
     return res
   
   }
   let obj1 = deepPlus(obj)
   console.log("obj", obj)
   console.log("obj1", obj1)