Three implementation methods of JS deep copy

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Three implementation methods of JS deep copy

1. Convert the object into JSON string form, and then convert it into a native JS object;

//_tmp和result是相互独立的，没有任何联系，有各自的存储空间。
let deepClone = function (obj) {
    let _tmp = JSON.stringify(obj);//将对象转换为json字符串形式
    let result = JSON.parse(_tmp);//将转换而来的字符串转换为原生js对象
    return result;
};

let obj1 = {
    weiqiujaun: {
        age: 20,
        class: 1502
    },
    liuxiaotian: {
        age: 21,
        class: 1501
    }
};

let test = deepClone(obj1);
console.log(test);

2. Use the for loop in JS to implement traversal and copying;

function deepClone(obj) {
    let result = typeof  obj.splice === "function" ? [] : {};
    if (obj && typeof obj === 'object') {
        for (let key in obj) {
            if (obj[key] && typeof obj[key] === 'object') {
                result[key] = deepClone(obj[key]);//如果对象的属性值为object的时候，递归调用deepClone,即在吧某个值对象复制一份到新的对象的对应值中。
            } else {
                result[key] = obj[key];//如果对象的属性值不为object的时候，直接复制参数对象的每一个键值到新的对象对应的键值对中。
            }

        }
        return result;
    }
    return obj;
}

let testArray = ["a", "b", "c", "d"];
let testRes = deepClone(testArray);
console.log(testRes);
console.log(typeof testRes[1]);

let testObj = {
    name: "weiqiujuan",
    sex: "girl",
    age: 22,
    favorite: "play",
    family: {brother: "son", mother: "haha", father: "heihei"}
};
let testRes2 = deepClone(testObj);
testRes2.family.brother = "weibo";
console.log(testRes2);

3. Use the "Array.prototype.forEach" method of the array to copy to achieve deep copy.

let deepClone = function (obj) {
    let copy = Object.create(Object.getPrototypeOf(obj));
    let propNames = Object.getOwnPropertyNames(obj);
    propNames.forEach(function (items) {
        let item = Object.getOwnPropertyDescriptor(obj, items);
        Object.defineProperty(copy, items, item);

    });
    return copy;
};

let testObj = {
    name: "weiqiujuan",
    sex: "girl",
    age: 22,
    favorite: "play",
    family: {brother: "wei", mother: "haha", father: "heihei"}
}
let testRes2 = deepClone(testObj);
console.log(testRes2);

Recommended tutorial: "JS Tutorial"

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