alternating background images

static/js/background.js

@@ -0,0 +1,8 @@
+      var num = (Math.floor(Math.random()*4));
+
+
+      var array = ['one', 'two', 'three', 'four'];
+
+      var elem = document.getElementById('main');
+
+      elem.classList.add(array[num]);