Updated code of sum.js to return null if there are only non-numeric inputs only.

Author: JorvanW

Sprint-1/implement/sum.js

@@ -1,8 +1,11 @@
 function sum(elements) {
   elements = elements.filter(element => typeof element === 'number');
-  let total = 0;
-
-  for (let element of elements) {
+   if (elements.length === 0) {
+    return null;}
+  
+    let total = 0;
+  
+    for (let element of elements) {
     total += element;
     // += means to add to the current value and assign as result
     // elements are individual items inside a collection (not just string)