function forEach(array, iteratee) {

    let index = -1;

    const length = array.length;

    while (++index < length) {

        iteratee(array[index], index);

    }

    return array;

}

​

function clone(target, map = new WeakMap()) {

    if (typeof target === 'object') {

        const isArray = Array.isArray(target);

        let cloneTarget = isArray ? [] : {};

​

        if (map.get(target)) {

            return map.get(target);

        }

        map.set(target, cloneTarget);

​

        if (isArray) {

          forEach(target, (value, index) => {

            cloneTarget[index] = value;

          })

        } else {

          forEach(Object.keys(target), (key, index) => {

            cloneTarget[key] = target[key];

          })

        }

        return cloneTarget;

    } else {

        return target;

    }

}

​

var MyObject = {

  description: 'Creates a deep copy of source, which should be an object or an array.',

  myNumber: 123456789,

  myBoolean: true,

  jayson: {

    stringify: 'JSON.stringify() method converts a JavaScript value to a JSON string....',

    parse: 'JSON.parse() method parses a JSON string...'

  }

};

​

var myCopy = null;

​