SOURCE

function cloneDeep(source, hash = new WeakMap()) {
    if (!isObject(source)) return source

    const root = Array.isArray(source) ? [] : {}

    const loopList = [
        {
            parent: root,
            key: undefined,
            data: source
        }
    ]

    while(loopList.length) {
        const { parent, key, data } = loopList.pop()

        let target = parent
        if (key !== undefined) {
            target = parent[key] = Array.isArray(data) ? [] : {}
        }

        if (hash.has(data)) {
            target = hash.get(data)
            continue
        }
        hash.set(data, target)

        for (let k in data) {
            if (Object.prototype.hasOwnProperty.call(data, k)) {
                if (isObject(data[k])) {
                    loopList.push({
                        parent: target,
                        key: k,
                        data: data[k]
                    })
                } else {
                    target[k] = data[k]
                }
            }
        }
    }

    return root

    // 判断是否对象类型
    function isObject(source) {
        return typeof source === 'object' && source !== null
    }
}

const data = {
    a: {
        b: {
            c: 1,
            d: [
                {c: 2},
                'ss'
            ]
        }
    }
}

const clone = cloneDeep(data)
console.log(clone)