Day 9 – Count Vowels in a String using JavaScript | DSA Challenge with Code & Explanation

 

🧠 Day 9: Count Vowels in a String – JavaScript Interview Prep

Welcome to Day 9 of the #CodeWithJaffer JavaScript DSA series! Today, we’ll solve a popular string-based interview problem: “Count the number of vowels in a given string.”

🔍 Problem Statement:

Write a JavaScript function that takes a string as input and returns the count of vowels (a, e, i, o, u) present in it.

✅ Example Input & Output:

// Input:
"CodeWithJaffer"

// Output:
5 vowels (o, e, i, a, e)

💡 Method 1: Using RegEx

function countVowels(str) {
  return (str.match(/[aeiou]/gi) || []).length;
}

✅ Explanation:

• /[aeiou]/gi matches all vowels (both uppercase and lowercase).
• match() returns an array of matches, or null if none.
• || [] ensures no error when match returns null.
• .length gives the count of vowels.

💡 Method 2: Using For-Loop

function countVowelsLoop(str) {
  let count = 0;
  const vowels = "aeiouAEIOU";
  for (let char of str) {
    if (vowels.includes(char)) {
      count++;
    }
  }
  return count;
}

✅ Explanation:

• Iterates over each character.
• Checks if it’s present in the vowels string.
• Increments count for every vowel match.

🎯 Output:

console.log(countVowels("CodeWithJaffer")); // ➡️ 5
console.log(countVowelsLoop("CodeWithJaffer")); // ➡️ 5

📌 Tips to Remember:

• Use regex for cleaner and faster solutions.
• Use loops when regex is restricted in interviews.
• Don’t forget to handle uppercase vowels.

#CodeWithJaffer | Stay consistent, keep practicing. Share your solution in comments below 👇

🔖 Labels/Tags:

JavaScript, DSA, Interview Prep, Coding Challenge, Frontend, Vowels in String, CodeWithJaffer