Javascript Array customMap(fn)

/**/*ww w  .j ava 2 s.co m*/
 * Function takes a callback.
 * @param fn => function
 */
Array.prototype.customMap = function(fn) {
 let results = [];
    for (let i = 0; i < this.length; i++) {
        results.push(fn(this[i]));
    }
 return results;
};