Added missing 'var' on variable declaration. (#35675)

curriculum/challenges/english/08-coding-interview-prep/data-structures/add-elements-at-a-specific-index-in-a-linked-list.english.md

@@ -61,18 +61,17 @@ function LinkedList() {
 
   this.add = function(element){
     var node = new Node(element);
-    if(head === null){
+    if (head === null){
         head = node;
     } else {
-        var currentNode = head;
+      var currentNode = head;
 
-        while(currentNode.next){
-            currentNode  = currentNode.next;
-        }
+      while (currentNode.next) {
+        currentNode = currentNode.next;
+      }
 
-        currentNode.next = node;
+      currentNode.next = node;
     }
-
     length++;
   };