16.深拷贝/浅拷贝

1. 浅拷贝：默认在改变新的数组的时候，也改变了原数组。

let obj = { name: "张三", age: 28 };
let qian = obj;
qian.name = "李四";
console.log(obj.name); //李四
console.log(qian.name); //李四

2. 深拷贝：

方式一：使用JSON.stringify()以及JSON.parse()：

let obj = { name: "张三", age: 28 };
let strObj=JSON.stringify(obj);
let deep=JSON.parse(strObj);
deep.name= "李四";
console.log(obj.name); //张三
console.log(deep.name); //李四

方式二;concat（数组）:

let arr1=['张三','王五']
let arr2=[]
let res=arr1.concat(arr2)
res[0]= "李四";
console.log(arr1[0]); //张三
console.log(res[0]); //李四

方式三：通过for in实现:

//data
let obj = { name: "张三", age: 28 };
//methods
deepCopy(val) {
    let newObj = {};
    for (let i in val) {
        newObj[i] = val[i];
    }
    return newObj;
}

方式四：递归:

//data
let obj = { name: "张三", age: 28 };
//methods
deepCopy(val) {
    //判断拷贝的要进行深拷贝的是数组还是对象，是数组的话进行数组拷贝，对象的话进行对象拷贝
    var newObj = Array.isArray(obj) ? [] : {};
    //进行深拷贝的不能为空，并且是对象
    if (val && typeof val === "object") {
        for (i in val) {
            if (val.hasOwnProperty(i)) {
                if (val[i] && typeof val[i] === "object") {
                    newObj[i] = deepCopy(val[i]);
                } else {
                    newObj[i] = val[i];
                }
            }
        }
    }
    return newObj;
}