getGrade.js

function getGrade (s1, s2, s3) {
  let mean = ((s1 + s2 + s3) / 3);
  let grade = '';
  
  (90 <= mean && mean <= 100) ? grade = 'A' : 0;
  (80 <= mean && mean < 90) ? grade = 'B' : 0;
  (70 <= mean && mean < 80) ? grade = 'C' : 0;
  (60 <= mean && mean < 70) ? grade = 'D' : 0;
  (0 <= mean && mean < 60) ? grade = 'F' : 0;
  return grade;
}

//Testing
console.log(getGrade(95,90,93))//, 'A'
console.log(getGrade(100,85,96))//, 'A'
console.log(getGrade(92,93,94))//, 'A'


console.log(getGrade(70,70,100))//, 'B'
console.log(getGrade(82,85,87))//, 'B'
console.log(getGrade(84,79,85))//, 'B'
console.log(getGrade(89,89,90))//, 'B'


console.log(getGrade(70,70,70))//, 'C'
console.log(getGrade(75,70,79))//, 'C'
console.log(getGrade(60,82,76))//, 'C'


console.log(getGrade(65,70,59))//, 'D'
console.log(getGrade(66,62,68))//, 'D'
console.log(getGrade(58,62,70))//, 'D'


console.log(getGrade(44,55,52))//, 'F'
console.log(getGrade(48,55,52))//, 'F'
console.log(getGrade(58,59,60))//, 'F'