Check the exam.js

/*
Description:
The first input array contains the correct answers to an exam, like ["a", "a", "b", "d"]. The second one is "answers" array and contains student's answers.

The two arrays are not empty and are the same length. Return the score for this array of answers, giving +4 for each correct answer, -1 for each incorrect answer, and +0 for each blank answer(empty string).

If the score < 0, return 0.

For example:

checkExam(["a", "a", "b", "b"], ["a", "c", "b", "d"]) → 6
checkExam(["a", "a", "c", "b"], ["a", "a", "b",  ""]) → 7
checkExam(["a", "a", "b", "c"], ["a", "a", "b", "c"]) → 16
checkExam(["b", "c", "b", "a"], ["",  "a", "a", "c"]) → 0
*/

const checkExam = (answers, responses) => {
  const score = responses.reduce((total, response, index) => {
    if (!response) return total
    if (response === answers[index]) return total + 4
    if (response !== answers[index]) return total - 1

    return total
  }, 0)

  return score > 0 ? score : 0
}