/**
 * @param {string} s
 * @return {string}
 */
function longestPalindrome(str) {
    let palindrome = "";

    if (str.length < 1) return palindrome;

    function _reverse(start, length) {
        return str.substr(start, length).split("").reverse().join("");
    }

    for (let i = 0; i < str.length; i++) {
        for (let j = 1; j <= str.length - i; j++) {
            if (str.substr(i, j) === _reverse(i, j)) {
                if (j > palindrome.length) {
                    palindrome = str.substr(i, j);
                }
            }
        }
    }

    return palindrome;
}