block3.diff

+const wait = (ms: number) => {
+  var start = new Date().getTime();
+  var end = start;
+  while (end < start + ms) {
+    end = new Date().getTime();
+  }
+};
+const expensiveSelector = () => wait(3000);
 
 const connectThis = connect(state => ({
   count: state,
+  expensiveData: expensiveSelector()
 }));