Find the largest palindrome number made from the product of two n digit numbers in JavaScript

Let us consider the number 9009. This is a special number in the sense that this is the largest palindrome number that can be formed by multiplying two 2-digit numbers (91 and 99).

We are required to write a JavaScript function that takes a number n (which specifies the number of digits). The function should simply find and return the largest palindrome number that can be formed by the multiplication of two n digit numbers.

Example

Following is the code −

const largestPalindromic = num => {
   let i, n, m, d, max, sup, limit, number = 0;
   for (i = 1; i < num; i += 1) {
      number = 10 * number + 9;
   };
   max = number;
   sup = 10 * number + 9;
   const isPalindromic = n => {
      let p = 0, q = n, r;
      while (n > 0) {
         r = n % 10;
         p = 10 * p + r;
         n = Math.floor(n / 10);
      };
      return p === q;
   };
   for (n = sup * sup, m = max * max; n > m; n -= 1) {
      if (isPalindromic(n)) {
         limit = Math.ceil(Math.sqrt(n));
         d = sup;
         while (d >= limit) {
            if (n % d === 0 && n / d > max) {
               return n;
            }
            d -= 1;
         }
      }
   };
}
console.log(largestPalindromic(3));

Output

Following is the output on console −

906609