longest palindromic substring

<script>
 
// A O(n^2) time and O(1) space program to
// find the longest palindromic substring
// easy to understand as compared to previous version.
 
// A utility function to print
// a substring str[low..high]
// This function prints the
// longest palindrome substring (LPS)
// of str[]. It also returns the
// length of the longest palindrome
function longestPalSubstr(str)
{
    let n = str.length; // calculating size of string
    if (n < 2)
        return n; // if string is empty then size will be 0.
                // if n==1 then, answer will be 1(single
                // character will always palindrome)
 
    let maxLength = 1,start=0;
    let low, high;
    for (let i = 0; i < n; i++) {
        low = i - 1;
        high = i + 1;
        while ( high < n && str[high] == str[i]) //increment 'high'                               
            high++;
     
        while ( low >= 0 && str[low] == str[i]) // decrement 'low'               
            low--;
     
        while (low >= 0 && high < n && str[low] == str[high]){
            low--;
            high++;
        }
 
        let length = high - low - 1;
        if (maxLength < length) {
            maxLength = length;
            start=low+1;
        }
    }
     
    document.write("Longest palindrome substring is: ");
    document.write(str.substring(start,maxLength+start));
    return maxLength;
}
 
// Driver program to test above functions
 
let str = "forgeeksskeegfor";
document.write("</br>","Length is: " + longestPalSubstr(str),"</br>");
 
// This is code is contributed by shinjanpatra
 
</script>