5. Longest Palindromic Substring - https://leetcode.com/problems/longest-palindromic-substring/submissions/

longest_palindrome_substring.js

var longestPalindrome = function(str) {
    let strLen = str.length;
    let maxLen = 0, leftResult = 0, rightResult = 0, index = 0;
    
    while(index < strLen){
        
        let left = index-1;
        
        while(left >= 0 && str[index] == str[left]){
            left--;
        }
        let right = index+1;
        while(right < strLen && str[index] == str[right]){
            right++;
        }
        
        let end = right;
        
        while(left >= 0 && right < strLen && str[left] == str[right]){
            left--;
            right++;
        }
        
        if(maxLen < right-left-1){
            maxLen = right-left-1
            leftResult = left+1;
            rightResult = right-1;
        }
        index = end
    }
    return str.substring(leftResult,rightResult+1);
};