深拷贝

 <script>
        const obj1 = {
            age:20,
            name:'lily',
            address:{
                city:'beijing'
            },
            arr:['a','b','c']
        }
        // const obj2 = obj1;
        const obj2 =  deepClone(obj1);
        obj2.address.city = 'shanghai';
        // console.log(obj1.address.city); //shanghai
        console.log(obj1.address.city);  //beijing

        /*obj == obj1{} 要拷贝的对象*/ 
        function deepClone(obj = {}){
            // obj 不是对象或者为空直接返回
            if(typeof obj !== 'object' || obj == null){
                return
            }
            //初始化返回结果
            let result;
            if(obj instanceof Array){
                result = [];  
            }else{
                result = {}
            }

            for(let key in obj){
                // 保证key不是原型属性
              if(obj.hasOwnProperty(key)){
                //递归调用（函数通过名字调用自己本身）
                result[key] = deepClone(obj[key])
              }
            }
            //返回结果
            return result;
        }
        
    </script>