longestPalindrome

let longestPalindrome = function (str) { if (str.length < 2 || str === str.split('').reverse().join('')) return str.length; function expand(l, r) { while (l >= 0 && r <= str.length && str[l] === str[r - 1]) { l--; r++; } return str.substring(l + 1, r - 1); } let result = 0; for (let i = 0; i < str.length - 1; i++) { result = Math.max(result, expand(i,i+1).length, expand(i,i+2).length); } return result; };