方法一，用JSON：

const list = [{name:'浅拷贝'}];
const listCopy = JSON.parse(JSON.stringify(list));
listCopy[0].name = '深拷贝';

优点：

• JSON可以解决数组和Object的深拷贝

缺点：

• 不支持 Date、正则、undefined、函数等数据
• 不支持引用（即环状结构）

方法二，用递归：

要点：

1. 递归
2. 判断类型
3. 检查循环引用
4. 不拷贝原型上的属性

const deepClone = (a, cache) => {
    if(!cache){
        cache = new Map() // 不要全局缓存，最好临时创建并递归传递
    }
    if (a instanceof Object){
        if (cache.get(a)){return cache.get(a)}
        let result
        if (a instanceof Function){
            if (a.prototype){
                result = function (){return a.apply(this, arguments)}
            }else {
                result = (...args) => {return a.call(undefined, ...args)}
            }
        }else if (a instanceof Array){
            result = []
        }else if (a instanceof Date){
            result = new Date(a - 0)
        }else if (a instanceof RegExp){
            result = new RegExp(a.source, a.flags)
        }else {
            result = {}
        }
        cache.set(a, result)
        for (let key in a){
            if (a.hasOwnProperty(key)){
                result[key] = deepClone(a[key], cache)
            }
        }
        return result
    }else {
        return a
    }
}
const a = {
    number: 1, bool: false, str: 'hi', empty1: undefined, empty2: null,
    array:[
        {name: 'frank', age: 18},
        {name: 'jacky', age: 19}
    ],
    date: new Date(2000,0,1,20,30,0 ),
    regex: /.(j|t)sx/i,
    obj: {name: 'frank', age: 18},
    f1: (a, b) => a + b,
    f2: function (a, b){return a + b}
}
a.self = a

const b = deepClone(a)
b.self === b // true
b.self = 'hi'
a.self !== 'hi' //true