easyFormat.ts

#!/usr/bin/env ts-node 

const grades: [number, string][] = [
  [96, 'A+'],
  [93, 'A' ],
  [90, 'A-'],
  [86, 'B+'],
  [83, 'B '],
  [80, 'B-'],
  [76, 'C+'],
  [73, 'C '],
  [70, 'C-'],
  [66, 'D+'],
  [63, 'D '],
  [60, 'D-'],
  [56, 'F+'],
  [53, 'F '],
  [ 0, 'F-'],
];

const easyFormat = (val: number) => {
  const [_, grade] = 
    grades.find(([threshold]) => val >= threshold)!;

  return grade;
}

console.log('A+', easyFormat(100));
console.log('A+', easyFormat(96));
console.log( 'B+', easyFormat(89));
console.log( 'C-', easyFormat(70));
console.log( 'C ', easyFormat(73));
console.log( 'C ', easyFormat(75));
console.log( 'D+', easyFormat(69));
console.log( 'F-', easyFormat(50));