character.js

function makeHash (arr) {
  var map = {}
  for (var i=0;i<arr.length;i++) {
    if (map.hasOwnProperty(arr[i])) {
      map[arr[i]] += 1
    } else {
      map[arr[i]] = 1
    }
  }
  return map
}

function canCharacterBeMade (char, map) {
  var digits = ('' + char).split('').map(function (digit) {
    return Number(digit)
  })

  var digitMap = makeHash(digits)
  var canBeMade = true
  var keys = Object.keys(digitMap)

  for(d of keys) {
    d = Number(d)
    if (!(map.hasOwnProperty(d) && map[d] >= digitMap[d])){
      canBeMade = false
    }
  }
  return canBeMade
}

function makeAlphabets (arr) {
  var map = makeHash(arr)
  var characters  = []

  for (i=65; i <= 90;i++) {
    if (canCharacterBeMade(i, map)) {
    	characters.push(String.fromCharCode(i))
    }
  }

  for (i=97; i <= 122;i++) {
    if (canCharacterBeMade(i, map)) {
      characters.push(String.fromCharCode(i))
    }
  }
  return characters
}


console.log(makeAlphabets([1, 0, 1, 0, 6,5]))