first-unique-character-in-a-string.js

/**
 * Problem: https://leetcode.com/problems/first-unique-character-in-a-string/
 * Time: O(n)
 * Space: O(1)
/**
 * @param {string} s
 * @return {number}
 */
 var firstUniqChar = function(s) {
  let map = new Map();
  for(let char of s) {
      map.set(char, map.get(char) + 1 || 1);
  }
  for(let i =0; i < s.length; i++) {
      if(map.get(s[i]) == 1) return i
  }
  return -1;
};