Expand Around Corner

var longestPalindrome = function(s) {
    const N = s.length;

    const expandAroundCorner = (left, right) => {
        while (0 <= left && right < N && MEET_CONDITION(left, right)) {
            if (max < right - left + 1) {
                // operation
            }
            left -= 1;
            right += 1;
        }
        return [ max ];
    }

    for (let i = 0; i < N; i += 1) {
        const [ oddMax] = expandAroundCorner(i, i);
        const [ evenMax ] = expandAroundCorner(i, i + 1);
    }
};