SOURCE

const obj = {
    a: 1,
    b: {
        c: 2,
        d: '111',
        e: new Date(),
        f: function() {
            return '1';
        }
    }
}
const t = {m: obj};
obj.k = t;

// function app() {
//     return ap() {

//     }
// }

function deepClone(obj, map=new Map()) {
    if (obj === null || typeof obj !== 'object') {
        return obj;
    }
    if (map.has(obj)) {
        return map.get(obj);
    }
    if (obj instanceof Function) {
        const res = new Function("return " + obj.toString())();
        return res;
    }
    if (obj instanceof Date) {
        const res = new Date();
        res.setTime(obj.getTime());
        return res;
    }
    if (obj instanceof RegExp) {
        const res = new RegExp(obj);
        return res;
    }
    if (obj instanceof Array || obj instanceof Object) {
        const cloneObj = Array.isArray(obj) ? [] : {};
        for (let key in obj) {
            if (obj.hasOwnProperty(key)) {
                if (typeof obj[key] === 'object' && obj[key] !== null) {
                    map.set(obj, cloneObj);
                }
                cloneObj[key] = deepClone(obj[key], map);
            }
        }
         return cloneObj;
    }
}

const newObj = deepClone(obj);
console.log(deepClone(obj));