anagram-n.js

function check(letterPool, word) {
  // S1
  const map = {}
  for (let i=0; i<letterPool.length; i++) {
    const character = letterPool[i]
    if (map[character] === undefined) {
      map[character] = 1
    } else {
      map[character] += 1
    }
  }
  
  // S2
  const charInWord = word.split('')
  for (let i=0; i<charInWord.length; i++) {
    const character = charInWord[i]
    if (map[character])  {
      map[character] -= 1
    } else {
      return false  
    }
  }
  
  return true
}