Check Palindrome Number in JavaScript

 A palindrome number is a number that remains the same when its digits are reversed.

For example:

• 121 → Reversed → 121
• 1331 → Reversed → 1331

Both are palindrome numbers.

In this example, we will write a JavaScript program to check whether a number is a palindrome or not without using built-in reverse methods.

   

 function checkPalindromeNumber(num) {

      let originalNumber = num;

      let reversedNumber = 0;

      while (num > 0) {

        let digit = num % 10;

        reversedNumber = reversedNumber * 10 + digit;

        num = Math.floor(num / 10);

      }

      if (originalNumber === reversedNumber) {

        console.log(originalNumber + " is a Palindrome Number");

      } else {

        console.log(originalNumber + " is not a Palindrome Number");

      }

    }

    checkPalindromeNumber(number);

Output

121 is a Palindrome Number

---

How the Code Works

Step 1: Store the Original Number

let originalNumber = num;

We store the original number because the value of num will change during the loop.

---

Step 2: Reverse the Number

while (num > 0)

The loop runs until the number becomes 0.

Inside the loop:

let digit = num % 10;

Gets the last digit of the number.

reversedNumber = reversedNumber * 10 + digit;

Builds the reversed number.

num = Math.floor(num / 10);

Removes the last digit from the number.

---

Step 3: Compare Both Numbers

if (originalNumber === reversedNumber)

If both numbers are equal, then the number is a palindrome.

---

Time Complexity

• Time Complexity: O(n)
• Space Complexity: O(1)

This solution is efficient because it uses only a loop and no extra arrays or string methods.