Longest palindromic string possible after removal of a substring

<script>
      // JavaScript Implementation of the
      // above approach
      // Function to find the longest palindrome
      // from the start of the String using KMP match
      function findPalindrome(C) {
        var S = C;
        S = reverse(S);

        // Append S(reverse of C) to C
        C = C + "&" + S;
        var n = C.length;
        var longestPalindrome = new Array(n).fill(0);
        longestPalindrome[0] = 0;
        var len = 0;
        var i = 1;

        // Use KMP algorithm
        while (i < n) {
          if (C[i] === C[len]) {
            len++;
            longestPalindrome[i] = len;
            i++;
          } else {
            if (len !== 0) {
              len = longestPalindrome[len - 1];
            } else {
              longestPalindrome[i] = 0;
              i++;
            }
          }
        }
        var ans = C.substring(0, longestPalindrome[n - 1]);
        return ans;
      }

      // Function to return longest palindromic
      // String possible from the given String
      // after removal of any subString
      function findAns(s) {
        // Initialize three Strings A, B AND F
        var A = "";
        var B = "";
        var F = "";

        var i = 0;
        var j = s.length - 1;
        var len = s.length;

        // Loop to find longest subStrings
        // from both ends which are
        // reverse of each other
        while (i < j && s[i] === s[j]) {
          i = i + 1;
          j = j - 1;
        }

        if (i > 0) {
          A = s.substring(0, i);
          B = s.substring(len - i, len);
        }

        // Proceed to third step of our approach
        if (len > 2 * i) {
          // Remove the subStrings A and B
          var C = s.substring(i, i + (s.length - 2 * i));

          // Find the longest palindromic
          // subString from beginning of C
          var D = findPalindrome(C);

          // Find the longest palindromic
          // subString from end of C
          C = reverse(C);
          var E = findPalindrome(C);

          // Store the maximum of D and E in F
          if (D.length > E.length) {
            F = D;
          } else {
            F = E;
          }
        }

        // Find the readonly answer
        var answer = A + F + B;

        return answer;
      }

      function reverse(input) {
        var a = input.split("");
        var r = a.length - 1;
        for (var l = 0; l < r; l++, r--) {
          var temp = a[l];
          a[l] = a[r];
          a[r] = temp;
        }
        return a.join("");
      }

      // Driver Code
      var str = "abcdefghiedcba";
      document.write(findAns(str));
      
      // This code is contributed by rdtank.
    </script>