Question

How to check if a word is all uppercase or lowercase or capitalized in TypeScript

Answer 1

function verifyAllUpperOrAllLowerOrIsCapitalized(word: string): boolean {
  let upper: number = 0;
  let lower: number = 0;

  for (const ch of word) {
    if (ch >= 'a' && ch <= 'z') {
      lower++;
    } else if (ch >= 'A' && ch <= 'Z') {
      upper++;
    }
  }

  // Case 1: all lowercase
  if (upper === 0) return true;

  // Case 2: all uppercase
  if (lower === 0) return true;

  // Case 3: capitalized (only first letter uppercase)
  if (upper === 1 && word[0] >= 'A' && word[0] <= 'Z') return true;

  // Otherwise, mixed casing
  return false;
}

function runTest(word: string): void {
  console.log(`Testing word: "${word}"`);
  if (verifyAllUpperOrAllLowerOrIsCapitalized(word)) {
    console.log("OK\n");
  } else {
    console.log("Error\n");
  }
}

runTest("PROGRAMMING");   
runTest("programming");   
runTest("Programming");   
runTest("ProGramMing");   



/*
run:
 
Testing word: "PROGRAMMING"
OK

Testing word: "programming"
OK

Testing word: "Programming"
OK

Testing word: "ProGramMing"
Error
 
*/

 

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