Added more helpful technique for accessing promise (#1124)

* Added more helpful technique for accessing promise

* Updated w/ feedback

* Add missing semicolon

live-examples/js-examples/promise/promise-constructor.html

@@ -1,9 +1,17 @@
 <pre>
 <code id="static-js">var promise1 = new Promise(function(resolve, reject) {
-  setTimeout(resolve, 100, 'foo');
+  setTimeout(function() { 
+    resolve('foo');
+  }, 300);
+});
+
+promise1.then(function(value) { 
+  console.log(value);
+  // expected output: "foo"
 });
 
 console.log(promise1);
 // expected output: [object Promise]
+
 </code>
 </pre>