LAITONEN

import _ from 'lodash';

// count duplicates in the array and return the object, where 'key' is a unique value from the array
// and value is a number of duplicates of this value in the array

export function countDuplicates (array) {
    const object = {};

    array.filter((v, i, a) => i === a.indexOf(v))
         .forEach(v => object[v] = object[v] ? object[v] + 1 : 1);

LAITONEN

const riddle = 'g fmnc wms bgblr rpylqjyrc gr zw fylb. rfyrq ufyr... amknsrcpq ypc dmp. bmgle gr gl zw fylb gq glcddgagclr ylb rfyrq... ufw rfgq rcvr gq qm jmle. sqgle qrpgle.kyicrpylq() gq pcamkkclbcb.... lmu ynnjw ml rfc spj.';
const alphabet = 'abcdefghijklmnopqrstuvwxyz';
const orderNumber = alphabet.split('').map((v, i) => {
	return { newIndex: i+2, letter: v };
})

const result = riddle.split('').map(v => {
	if (/[a-z]/.test(v)) {
		return orderNumber[orderNumber[alphabet.indexOf(v)].newIndex].letter;
    	}