深拷贝和浅拷贝

浅拷贝: 只拷贝一层， 对更深层次对象只拷贝了地址
深拷贝: 层层拷贝， 对每一层级的数据都进行拷贝
实现浅拷贝的方法:
方法一:

let obj = {
  id: 1,
  name: 'Andy',
  msg: {
    age: 18
  }
}

let newObj = {};
for (const key in obj) {
  newObj[key] = obj[key];
}
obj.msg.age = 19;
console.log('====================================');
console.log('newObj', newObj, 'obj', obj);
console.log('====================================');

方法二:

let newObj = {};
Object.assign(newObj, obj);
obj.msg.age = 19;
console.log('====================================');
console.log('newwObj', newObj, 'obj', obj);
console.log('====================================');

方法三：

let newObj = {...obj};
obj.msg.age = 20;
console.log('====================================');
console.log('newObj', newObj, 'obj', obj);
console.log('====================================');

方法四:

let newObj = obj;
obj.msg.age = 20;
console.log('====================================');
console.log('浅拷贝', 'newObj', newObj, 'obj', obj, newObj === obj);
console.log('====================================');

实现深拷贝的方法:

let obj = {
  id: 1,
  name: 'Andy',
  msg: {
    age: 18
  },
  likeAuthor: ['刘同', '张嘉佳']
}

let newObj = {};
function deepCopy(newObj, obj) {
  for (const key in obj) {
    if(obj[key] instanceof Array) {
      newObj[key] = [];
      deepCopy(newObj[key], obj[key])
    }else if(obj[key] instanceof Object) {
      newObj[key] = {};
      deepCopy(newObj[key], obj[key])
    }else {
      newObj[key] = obj[key];
    }
  }
}

deepCopy(newObj, obj);
obj.msg.age = 20
console.log('====================================');
console.log('newObj', newObj, 'obj', obj);
console.log('====================================');