JavaScript task: Find longest palindrome of the string "hellonevenlikestacocatandkayak"

longestPalindrome.js

function is_Palindrome(str1) {
    var rev = str1.split("").reverse().join("");
    return str1 == rev;
}

function longest_palindrome(str1){

    var max_length = 0,
    maxp = '';

    for(var i=0; i < str1.length; i++) 
    {
        var subs = str1.substr(i, str1.length);

        for(var j=subs.length; j>=0; j--) 
        {
            var sub_subs_str = subs.substr(0, j);
            if (sub_subs_str.length <= 1)
                continue;

            if (is_Palindrome(sub_subs_str))
            {
                if (sub_subs_str.length > max_length) 
                {
                    max_length = sub_subs_str.length;
                 maxp = sub_subs_str;
                }
            }
        }
    }

    return maxp;
}
console.log(longest_palindrome("hellonevenlikestacocatandkayak"))