js深拷贝

功能如下：

1. WeakMap 解决循环引用问题
2. 支持拷贝的数据类型：

• • 基本数据类型：number、string、boolean、undefined、null、symbol
  • 引用数据类型：Date、RegExp、Function、Object、Map、Set

代码实现：

　　

function clone(obj, map = new WeakMap) {
    if (map.has(obj)) return map.get(obj);
    if (obj === null) {
        return null;
    }
    let result = {};
    if (Array.isArray(obj)) {
        result = [];
    }
    if (obj instanceof RegExp || obj instanceof Date) {
        result = new obj.constructor(obj);
        map.set(obj, result);
    }
    if (obj instanceof Map || obj instanceof Set) {
        result = new obj.constructor();
        map.set(obj, result)
        if (obj instanceof Map) {
            obj.forEach((val, key) => {
                result.set(key, clone(val, map));
            });
        } else {
            obj.forEach((val, key) => {
                result.add(clone(val, map));
            });
        }
        // 由于Map、Set的typeof 为object，这里需要return;
        return result;
    }
    if (obj instanceof Function) {
        result = () => { obj() };
        map.set(obj, result)
    }
    if (['number', 'string', 'boolean'].includes(typeof obj)) {
        result = obj;
    }
    if (typeof obj === 'object') {
        result = Object.create(Reflect.getPrototypeOf(obj), Object.getOwnPropertyDescriptors(obj), Object.getOwnPropertySymbols(obj));
        map.set(obj, result)
        Reflect.ownKeys(obj).forEach(key => {
            result[key] = clone(obj[key], map);
        });
    }
    return result;
}

测试代码：

const mapA = new Map();
mapA.set('a', 'aaa');
const setA = new Set();
setA.add(1,2,3);
const sym = Symbol('m');
const obj = {
    a: 1,
    b: '1',
    c: true,
    d: undefined,
    e: null,
    f: new Date(),
    g: new RegExp(),
    h: function(){
        console.log('111')
    },
    i: {i: '1', ii: {ii: '11'}},
    j: [1,2,3, {j: 'j', jj: 'jj'}],
    k: mapA,
    l: setA,
    [sym]: 'm'
}
const newObj = clone(obj);