/**
 * @param {string} s
 * @return {number}
 */
function firstUniqChar(s) {
  const arr = Array.from([...s]
                         .reduce((map, x, i) => map.set(x, !isNaN(map.get(x)) ? null : i) , new Map())
                         .values());
  for(let i = 0; i < arr.length; i++) {
    if (arr[i] !== null) { return arr[i]; }
  }
  return -1;
};