手搓深拷贝

const obj = {
   
  name: "tom",
  age: 19,
  hobby: ["篮球", "排球"],
  sayhi() {
   
    console.log("sayhi");
  },
  info:{
   
    name:'jerry',
    age: 20
  }
};
const o = {
   };
//在写Object和Array的判断条件时，数组必须写在对象的前面。因为数组也是一种对象
function fn(newObj, oldObj) {
   
  for (const key in oldObj) {
   
    if (!newObj[key]) {
   
      // Array
      if (oldObj[key] instanceof Array) {
   
        newObj[key] = []
        fn(newObj[key], oldObj[key]);
      }
      // Object
      else if(oldObj[key] instanceof Object) {
   
        newObj[key] = {
   }
        fn(newObj[key], oldObj[key]);
      }
      else {
   
        newObj[key] = oldObj[key];
      }
    }
  }
}
fn(o, obj);
o.hobby[0] = '乒乓球'

o.info.age = '22'
console.log(o);
/*{ name: 'tom', age: 19, hobby: [ '乒乓球', '排球' ], sayhi: {}, info: { name: 'jerry', age: '22' } }*/
console.log(obj);
/*{ name: 'tom', age: 19, hobby: [ '篮球', '排球' ], sayhi: [Function: sayhi], info: { name: 'jerry', age: 20 } }*/