Add recursive and dynamic programming solution to fibonacci

fibonacci/fibonacci.js

@@ -1,6 +1,6 @@
 const fibonacci = function(count) {
   if (count < 0) return "OOPS";
-  if (count === 0) return 0;
+  if (count == 0) return 0;
   let a = 0;
   let b = 1;
   for (let i = 1; i < count; i++) {
@@ -11,4 +11,25 @@ const fibonacci = function(count) {
   return b;
 };
 
+/* naive recursive */
+const fibonacciRecursive = function(count) {
+  if (count < 0) return 'OOPS';
+  if (count == 0) return 0;
+  if (count == 1) return 1;
+  return fibonacciRecursive(count - 1) + fibonacciRecursive(count - 2);
+}
+
+/* Dynamic Programming (DP) recursive */
+const fibonacciDp= function(count) {
+  return fibonacciDpHelper(count, {'0': 0, '1': 1});
+}
+
+const fibonacciDpHelper = function(count, memo) {
+  if (count < 0) return 'OOPS';
+  if (memo.hasOwnProperty(`${count}`)) return memo[`${count}`];
+  const result = fibonacciDpHelper(count - 1, memo) + fibonacciDpHelper(count - 2, memo);
+  memo[`${count}`] = result;
+  return result;
+}
+
 module.exports = fibonacci;