Add comments explaining switch block

Author: eddiemonge

page/javascript-101/conditional-code.md

@@ -115,12 +115,13 @@ var stuffToDo = {
 
 };
 
+// Check if the property exists in the object.
 if ( stuffToDo[ foo ] ) {
-
+	// This code won't run.
 	stuffToDo[ foo ]();
 
 } else {
-
+	// This code will run.
 	stuffToDo[ "default" ]();
 
 }