深拷贝

<script>
    function toType(obj) {
        return ({}).toString.call(obj).split(' ')[1].replace(']', '').toLowerCase()
    }
    function shallowClone(obj) {
        let type = toType(obj),
            Ctor = obj.constructor
        if (/^(symbol|bigint)$/i.test(type)) {
            return Object(obj)
        }
        if (/^(regexp|date)$/i.test(type)) {
            return new Ctor(obj)
        }
        if (/^(error)$/i.test(type)) {
            return new Ctor(obj.message)
        }
        if (/^function$/i.test(type)) {
            return function () {
                obj.call(this, ...arguments)
            }
        }
        if (/^(object|array)$/i.test(type)) {
            let keys = [...Object.keys(obj), ...Object.getOwnPropertySymbols(obj)]
            var result = new Ctor()
            keys.forEach(i => {
                result[i] = obj[i]
            })
            return result
        }
        return obj
    }

    function deepClone(obj, cache = []) {
        if (!/^(object|array)$/i.test(toType(obj))) {
            return shallowClone(obj)
        }
        if (!cache.includes(obj)) {
            cache.push(obj)
        } else {
            return obj
        }
        let Ctor = obj.constructor,
            result = new Ctor(),
            keys = [...Object.keys(obj), ...Object.getOwnPropertySymbols(obj)]
        keys.forEach(i => {
            result[i] = deepClone(obj[i], cache)
        })
        return result
    }

    var obj = {
        0: 'math',
        1: 'chinese',
        2: 'elglish',
        score: {
            math: 98,
            chinese: 100,
            elglish: 19,
        },
        reg: /\d+/,
        time: new Date,
        friends: ['tom', 'jerry'],
        say: function () {
            console.log('good good study!');
        },
        tag: Symbol('TAG'),
        [Symbol.toStringTag]: 'object'
    };

    obj.xxx = obj
    var obj1 = deepClone(obj)

</script>