creating init function

app.js

@@ -95,6 +95,7 @@ var formatTime = d3.timeFormat("%B%e, %Y at %-I:%M%p");
 var lastTransform = null;
 var zoom = d3.zoom().on('zoom', zoomCallback);
 
+var init = function(){
     d3.select('#container')
         .style('width', WIDTH)
         .style('height', HEIGHT);
@@ -148,3 +149,6 @@ d3.select('#container').on('click', function(){
     });
 
     d3.select('#container').call(zoom);
+}
+
+init();