[JavaScript知识库]js-浅拷贝和深拷贝

 let obj = {
        name: "张三",
        age: 18
    }
    let user = obj
    user.name = "李思"
    console.log(obj);
    console.log(user);

?

?

user和obj的地址是同一个，所以user修改了name的值也会影响obj的name值

浅拷贝

由此出现了浅拷贝：其作用就是用于解决数据共享的问题

方式1：合并对象，Object.assign({},对象),第一个参数必须是空对象，为了得到一个新的地址

let obj = {
        name: "张三",
        age: 12,
        sex: "男"
    }
    let user = Object.assign({}, obj)
    user.name = "李华"
    console.log(obj);
    console.log(user);

?

?

方式2：for...in遍历对象，?先声明一个空的对象，得到一个新的地址

 let obj = {
        name: "张三",
        age: 12,
        sex: "男"
    }
    let user = {}
    for (const key in obj) {
        user[key] = obj[key]
    }
    user.name = "李华"
    console.log(obj);
    console.log(user);

深拷贝

解决浅拷贝只能拷贝一层的问题

方式1：JSON的两个核心方法--可以解决95%的问题，例如undefined，null,NaN,Infinity函数等进行深拷贝都会导致内容丢失

 let obj = {
        name: "张三",
        age: 12,
        sex: "男",
        likes: ["篮球", "睡觉"],
        cuser: {
            name: "张无忌",
            job: "it"
        }
    }
    let user = JSON.parse(JSON.stringify(obj))

    user.cuser.job = "java"
    user.likes.push("游戏")
    user.name = "李华"
    console.log(obj);
    console.log(user);

方式2：Lodash解决方式1的解决不了的问题

<script src="./lodash.js"></script>
<script>
    let obj = {
        name: "张三",
        age: 12,
        sex: "男",
        money: Infinity,
        b: NaN,
        likes: ["篮球", "睡觉"],
        cuser: {
            name: "张无忌",
            job: "it"
        }
    }
    let user = _.cloneDeep(obj)
    user.cuser.job = "java"
    user.likes.push("游戏")
    user.name = "李华"
    console.log(obj);
    console.log(user);
</script>