diff --git a/script/single.js b/script/single.js
index 5214d41..aeaf9b7 100644
--- a/script/single.js
+++ b/script/single.js
@@ -1,5 +1,7 @@
 'use strict';
 
+(function() {
+
 function defined(x) {
   return x !== null && typeof x !== 'undefined';
 }
@@ -53,4 +55,6 @@ function setup() {
   }
 }
 
-window.onload = setup;
+window.addEventListener('load', setup);
+
+})();