Randomly scrambles the given username.

scramble-name.js

/**
 * Randomly scrambles the given username.
 * @param   {String} realName The username to be scrambled.
 * @returns {String} The scrambled username.
 */
function scrambleName(realName) {
  "use strict";

  var newName  = "",
      usedChar = [];

  function randomLetter(myString) {
   return Math.floor(Math.random() * myString.length);
  }

  for (var i = 0; i < realName.length; i++) {
    var letterIndex = randomLetter(realName);

    // That letter has already been used
    while (usedChar.indexOf(letterIndex) > -1) {
      letterIndex = randomLetter(realName);
    }

    usedChar.push(letterIndex);
    newName += realName.charAt(letterIndex);
  }
  return newName;
}

scrambleName("le717");