Trello developer task

index.js

#!/usr/bin/node
/**
 * Trello task description: https://trello.com/jobs/developer
 */

/**
 * @function hash Create hash from string
 * @param {String} str String to hash
 * @return {Number} hash
 */
function hash (str) {
  var h = 7;
  var letters = "acdegilmnoprstuw";
  for (var i = 0; i < str.length; i++) {
    h = (h * 37 + letters.indexOf( str[i] ));
  }

  return h;
}

/**
 * @function deHash Get string from hash
 * @param {Number} hash Hash to string
 * @param {Number} L Lenght of string
 * @return {String} string
 */
function deHash (hash, L) {
  var letters = "acdegilmnoprstuw";
  var str = '';
  var hashList = [];
  var index = null;

  for (var i = 0; i < L; i++) {
    hashList.push(parseInt(hash));
    hash = hash/37;
  }
 
  for (var j = hashList.length-1; j >= 0; j--) {
    if (j !== L-1) {
      index = hashList[j] - hashList[j+1]*37;
    } else {
      index = hashList[j] - 7*37;
    }

    str += letters[index];
  }

  return str;
}

var hash7 = hash('leepadg');
var deHash7 = deHash(hash7, 7);
console.assert('leepadg' == deHash7, 'Hashing `leepadg` failed');
console.log( 'Test `leepadg` ok' );

var deHash9 = deHash(956446786872726, 9);
var hash9 = hash(deHash9);
console.assert(956446786872726 == hash9, 'Deashing `956446786872726` failed');
console.log( 'Test `956446786872726` ok\n' );

console.log( 'Answer: %s', deHash9 );