测试

好了，到目前为止，我们基本上实现了一个功能较为完整的深拷贝。最终的实现函数如下：

function deepClone(target, cache = new Map()) {   
    if (cache.get(target)) {
        return cache.get(target);
    }
    if (target instanceof Object) {
        let dist;
        if (target instanceof Array) {
            //拷贝数组
            dist = [];
        } else if (target instanceof Function) {
            //拷贝函数
            dist = function() {
                return target.call(this, ...arguments);
            }
        } else if (target instanceof RegExp) {
            //拷贝正则
            dist = new RegExp(target.source, target.flags);
        } else if (target instanceof Date) {
            //拷贝日期
            dist = new Date(target);
        } else {
            //拷贝普通对象
            dist = {};
        }
        //将属性和拷贝后的值作为一个Map
        cache.set(target, dist);
        for (let key in target) {
            //过滤调原型上的属性
            if (target.hasOwnProperty(key)) {
                dist[key] = deepClone(target[key], cache);
            }
        }
        return dist;
    } else {
        return target;
    }
}

接下来我们就写一个复杂的对象，使用这个对象进行深拷贝，测试我们的函数性能。

const a = {
    i: Infinity,
    s: "",
    bool: false,
    n: null,
    u: undefined,
    sym: Symbol(),
    obj: {
        i: Infinity,
        s: "",
        bool: false,
        n: null,
        u: undefined,
        sym: Symbol(),
    },
    array: [{
            nan: NaN,
            i: Infinity,
            s: "",
            bool: false,
            n: null,
            u: undefined,
            sym: Symbol(),
        },
        123,
    ],
    fn: function() {
        return "fn";
    },
    date: new Date(),
    re: /hi\d/gi,
};
let a2 = deepClone(a);
console.log(a2 !== a);
console.log(a2.i === a.i);
console.log(a2.s === a.s);
console.log(a2.bool === a.bool);
console.log(a2.n === a.n);
console.log(a2.u === a.u);
console.log(a2.sym === a.sym);
console.log(a2.obj !== a.obj);
console.log(a2.array !== a.array);
console.log(a2.array[0] !== a.array[0]);
console.log(a2.array[0].i === a.array[0].i);
console.log(a2.array[0].s === a.array[0].s);
console.log(a2.array[0].bool === a.array[0].bool);
console.log(a2.array[0].n === a.array[0].n);
console.log(a2.array[0].u === a.array[0].u);
console.log(a2.array[0].sym === a.array[0].sym);
console.log(a2.array[1] === a.array[1]);
console.log(a2.fn !== a.fn);
console.log(a2.date !== a.date);
console.log(a2.re !== a.re);