added answers

03_reverseString/reverseString.js

@@ -1,5 +1,9 @@
-const reverseString = function() {
-
+const reverseString = function(string) {
+    let reversed = "";
+for(let i = string.length - 1; i >= 0; i--){
+    reversed+=string[i];
+}
+return reversed;
 };
 
 // Do not edit below this line