Check the exam

//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

//My code

function checkExam(array1, array2) {
var score = 0;
  
  for (var i = 0; i < array1.length; i++){
  
    if (array1[i] == array2[i]) {
    
    score += 4;
    
    }
    
    else if (array2[i] === ""){

      score += 0
  
    }
    
     
    else {
    
    score -= 1
    
    }

  
  }
  
  if (score < 0) {
  
    score = 0
    
  }  
 
 return score