Finding unique characters in a string

by mattography

JavaScript

function findUnique(str) {
  var i, ch;
  var len = str.length;
  var freqMap = new Map();
  var uniq = '';

  for (i = 0; i < len; i++) {
    ch = str[i];
    if (!freqMap.get(ch)) {
      freqMap.set(ch, 1);
    } else {
      freqMap.set(ch, -1);
    }
  }

  freqMap.forEach(function(val, key) {
    if (val == 1) {
      uniq += key;
    }
  });

  return uniq;
}