palindrome.js

function biggestPalindrome (str) {
    if (str.length === 1) return str;
    const pieces = str.split('');
    let longestPalindrome = '';
    for (let i = 1; i <= pieces.length; i++) {
        let offset = 1;
        do {
            if (pieces[i-offset] === pieces[i+offset]) {
                const newPalindrome = str.substring(i-offset, i+offset+1);
                if (newPalindrome.length > longestPalindrome.length) longestPalindrome = newPalindrome;
                offset++;
                continue
            } 
            if (pieces[i-offset] === pieces[i+(offset-1)]) {
                const newPalindrome =  str.substring(i-offset, i+(offset));
                if (newPalindrome.length > longestPalindrome.length) longestPalindrome = newPalindrome;
                offset++;
                continue
            } 
            break;
        } while (offset < 100);
    }
    return longestPalindrome;
}