Find the first unrepeated char in a string. http://programmingpraxis.com/2013/04/30/first-unrepeated-character-in-a-string/

unrepeated_char.js

function firstUnrepeated(str) {
  var blacklist = [];
  var once = {};
  str.split("").forEach(function(e, pos) {
    if (blacklist.indexOf(e) === -1) {
      once[e] = pos;
      blacklist.push(e);
    }
    else { delete once[e]; }
  });

  return Object.keys(o).reduce(function(prev, cur) {
    if (!o[prev] || o[cur][1] < o[prev][1])
      return cur;

    return prev;
  }, null)
}