let obj1 = {
    name: ‘张三‘,
    age: undefined,
    see: function(){
       console.log("看");
    },
    son: {
       name: ‘张四‘
    }
}
let obj2 = JSON.parse(JSON.stringify(obj1));

function deepClone(target){
    if(target === null) return   null;
    if(typeof target !== ‘object‘) return target;
    const cloneTarget = Array.isArray(target) ? [] : {};
    for( let prop in target){
       if(target.hasOwnProperty(prop)){
           cloneTarget[prop] = deepClone(target[prop]);
       }
    }
    return cloneTarget;  
}