Verification if a number is Palindrome in JavaScript

Let’s say, we have to write a function that takes in a Number and returns a boolean based on the fact whether or not the number is palindrome. One restriction is that we have to do this without converting the number into a string or any other data type.

Palindrome numbers are those numbers which read the same from both backward and forward.

For example −

121
343
12321

Therefore, let’s write the code for this function −

Example

const isPalindrome = (num) => {
   // Finding the appropriate factor to extract the first digit
   let factor = 1;
   while (num / factor >= 10){
      factor *= 10;
   }
   while (num) {
      let first = Math.floor(num / factor);
      let last = num % 10;
      // If first and last digit not same return false
      if (first != last){
         return false;
      }
      // Removing the first and last digit from number
      num = Math.floor((num % factor) / 10);
      // Reducing factor by a factor of 2 as 2 digits are dropped
      factor = factor / 100;
   }
   return true;
};
console.log(isPalindrome(123241));
console.log(isPalindrome(12321));
console.log(isPalindrome(145232541));
console.log(isPalindrome(1231));

Output

The output in the console will be −

false
true
true
false

AmitDiwan

e

Updated on: 21-Aug-2020

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