JavaScript Program to Count Vowels and Consonants in a String

Counting vowels and consonants in a string is a classic string-processing exercise: loop through each character, check whether it’s a letter, and classify it as a vowel (a, e, i, o, u) or a consonant.

JavaScript Program to Count Vowels and Consonants in a String

function countVowelsAndConsonants(str) {
  const vowels = "aeiouAEIOU";
  let vowelCount = 0;
  let consonantCount = 0;

  for (const char of str) {
    if (!/[a-zA-Z]/.test(char)) continue; // skip spaces, digits, punctuation

    if (vowels.includes(char)) {
      vowelCount++;
    } else {
      consonantCount++;
    }
  }

  return { vowelCount, consonantCount };
}

const result = countVowelsAndConsonants("Simple2Code JavaScript Tutorials");
console.log(`Vowels: ${result.vowelCount}, Consonants: ${result.consonantCount}`);

Output:

Vowels: 11, Consonants: 18

The for...of loop here walks the string one character at a time, the same idea as reversing a string character by character. The regular expression /[a-zA-Z]/ filters out anything that isn’t a letter, so digits and spaces in the input don’t get miscounted as consonants — a common bug in naive versions of this program. You can extend this same pattern to also count digits and special characters by adding similar checks inside the loop.