SOURCE

// 深拷贝简易方式：
function deepClone(obj) {
    if (typeof obj === 'object') {
        var newObj = obj.constructor === Array ? [] : {}
        for (var i in obj) {
            newObj[i] = typeof obj[i] === 'object' ? deepClone(obj[i]) : obj[i]
        }
    } else {
        var newObj = obj
    }
    return newObj
}

// 深拷贝hash方式：
function isObject(o) {
    return Object.prototype.toString.call(o) === "[object Object]" ||
        Object.prototype.toString.call(o) === "[objectArray]"
}
function deepClone4(o, hash = new Map()) {
    if (!isObject(o)) return o //检测是否为对象或者数组
    if (hash.has(o)) return hash.get(o)
    let obj = Array.isArray(o) ? [] : {}
    hash.set(o, obj)
    console.log('hhhh',hash)
    for (let i in o) {
        if (isObject(o[i])) {
            obj[i] = deepClone4(o[i], hash)
        } else {
            obj[i] = o[i]
        }
    }
    return obj
}

var a = {};
a.a = a;
var bb = deepClone4(a)
console.log(bb)