怎样拷贝数组 深拷贝 / 浅拷贝

Question

拷贝数组就是把原来数组的每一项保存在一个新数组中，这样在操作数组的同时，另一个数组就不会受影响，因为数组是引用类型的值，所以在拷贝数组的同时并不能直接复制变量值，我们有一下几种方法可以使用。

循环

var ary1 = [1,2,3];

for (var i = 0, ary2 = Array(ary1.length); i < ary1.length; i++) ary2[i] = ary1[i];

slice

var ary1 = [1,2,3];

var ary2 = ary1.slice();

运算符

var ary1 = [1,2,3];

var ary2 = [...ary1];

from

var ary1 = [1,2,3];

var ary2 = Array.from(ary1);

concat

var ary1 = [1,2,3];

var ary2 = [].concat(ary1);

说到深拷贝，比较特殊的就是数组和对象了，所以在编写方法的时候要分别做不同的处理，代码如下：

let ary = [1,[2, {name: "张三"}]];

function copyAry(options) {
    return copy(options)
}

function copy(ary) {
    let newAry = []
    for (const item of ary) {
        let value = item;
        if (Object.prototype.toString.call(value) === "[object Object]") value = copyObj(value);
        if (Object.prototype.toString.call(value) === "[object Array]") value = copyAry(value);
        newAry.push(value);
    }
    return newAry;
}

function copyObj(obj) {
    let newObj = {};
    for (const key in obj) {
        let value = obj[key];
        if (Object.prototype.toString.call(value) === "[object Object]") value = copyObj(value);
        if (Object.prototype.toString.call(value) === "[object Array]") value = copyAry(value);
        newObj[key] = value;
    }
    return newObj;
}

// 测试
let newAry = copyAry(ary);
ary[1][1].name="李四"
console.log(newAry[1][1].name) //张三
console.log(ary[1][1].name) //李四