Find First Unique Character In String

findFirstUniqueCharacterInString.js

function findUniqueCharacter(string) {
  const characterMap = buildCharacterMap(string);
  return findFirstUniqueCharacterInMap(characterMap);
}

function buildCharacterMap(string) {
  return string.split('').reduce((map, character) => {
    if (!map[character]) {
      map[character] = 1;
    } else {
      map[character]++; 
    }
    return map;
  }, {});
}

function findFirstUniqueCharacterInMap(characterMap) {
  const characters = Object.keys(characterMap);
  for (let i = 0; i < characters.length; i++) {
    if (characterMap[characters[i]] === 1) {
      return characters[i];
    }
  }
  return '_';
}

const firstUniqueCharacter = findUniqueCharacter('stringgoeshere');