check_the_exam.js

/*
The first input array is the key to the correct answers to an exam, like ["a", "a", "b", "d"]. The second one contains a student's submitted 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, represented as an empty string (in C the space character is used).

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

*/

function checkExam(array1,array2) {
  let score = 0
  for(i=0;i<array1.length;i++) {
    if(array1[i] === array2[i]) {score += 4} 
    else if(array2[i] === '') {score +=0} 
    else{score -= 1}
	}
  return score<0? 0:score
}