New javascript solution to problem 5 and updated readme

README.md

@@ -557,7 +557,7 @@ LeetCode
 |8|[String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)| [C++](./algorithms/cpp/stringToIntegerAtoi/stringToIntegerAtoi.cpp)|Easy|
 |7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)| [C++](./algorithms/cpp/reverseInteger/reverseInteger.cpp)|Easy|
 |6|[ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)| [C++](./algorithms/cpp/zigZagConversion/zigZagConversion.cpp)|Easy|
-|5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)| [C++](./algorithms/cpp/longestPalindromicSubstring/longestPalindromicSubstring.cpp)|Medium|
+|5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)| [C++](./algorithms/cpp/longestPalindromicSubstring/longestPalindromicSubstring.cpp), [Javascript](./algorithms/javascript/longestPalindromicSubstring/longestPalindromicSubstring.js)|Medium|
 |4|[Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)| [C++](./algorithms/cpp/medianOfTwoSortedArrays/medianOfTwoSortedArrays.cpp)|Hard|
 |3|[Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)| [C++](./algorithms/cpp/longestSubstringWithoutRepeatingCharacters/longestSubstringWithoutRepeatingCharacters.cpp)|Medium|
 |2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)| [C++](./algorithms/cpp/addTwoNumbers/addTwoNumbers.cpp)|Medium|

algorithms/javascript/longestPalindromicSubstring/longestPalindromicSubstring.js

@@ -0,0 +1,25 @@
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function(s) {
+    // ll: Left index of the longest palindrome.
+  // rr: Right index of the longest palindrome.
+  let ll = 0, rr = 0;
+
+  // Iterate all palindromes with center indices
+  // [..., i, ...] or [... i, i+1, ...]
+  for (let i = 0; i < s.length; i++) {
+    for (let j of [i, i+1]) {
+        // console.log(j);
+      for (l = i, r = j; s[l] && s[l] === s[r]; l--, r++)
+
+        // Found a new palindrome [l, ..., i, j, ..., r]
+        // Update the ll, rr if the newly found palindrome is longer than the
+        // existing one.
+        [ll, rr] = (r-l+1) > (rr-ll+1) ? [l, r] : [ll, rr];
+        // console.log(ll + ' + ' + rr);
+    }
+  }
+  return s.substring(ll, rr+1);
+};