Discussion on: If-Else or Switch-Case: Which One to Pick?

[peerreynders]

TypeScript supports exhaustiveness checking on union types.

type Grade = 'A+' | 'A' | 'B+' | 'B' | 'C' | 'D' | 'F';

function studentFinalResult(grade: Grade): string {
  switch (grade) {
    case 'A+':
      return 'Nailed It! 🥳';
    case 'A':
    case 'B+':
    case 'B':
      return 'Passed 💃';
    case 'C':
      return 'Barely Survived 😌';
    case 'D':
    case 'F':
      return 'Failed 😢';
    default:
      const _exhaustiveCheck: never = grade; // "Type 'string' is not assignable to type 'never'".
      return _exhaustiveCheck;               // if one of the union type values is missing
  }
}

console.log(studentFinalResult('A+')); // "Nailed It! 🥳"

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