Exercise 4: track mouse moves across P elements.

Chapter 3/03.js

@@ -105,4 +105,15 @@ $(document).ready(function () {
     var nextClass = triggerValues[nextIndex];
     setBodyClass(nextClass);
   });
+
+  // Exercise 4.
+  var tracker = function(event) {
+      console.log(event.pageX, event.pageY);
+  };
+  $('p').mouseenter(function (event) {
+    $(this).mousemove(tracker);
+  }).mouseleave(function (event) {
+    $(this).off('mousemove');
+  });
+
 });