Try Dart 1 hour experience first draft

src/site/codelabs/darrrt/examples/3-buttonbadge/piratebadge.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:html';
+
+ButtonElement genButton;
+
+void  main() {
+  querySelector('#inputName').onInput.listen(updateBadge);
+  genButton = querySelector('#generateButton');
+  genButton.onClick.listen(generateBadge);
+}
+
+void updateBadge(Event e) {
+  String inputName = (e.target as InputElement).value;
+  
+  setBadgeName(inputName);
+  if (inputName.trim().isEmpty) {
+    genButton..disabled = false
+             ..text = 'Aye! Gimme a name!';
+  } else {
+    genButton..disabled = true
+             ..text = 'Arrr! Write yer name!';
+  }
+}
+
+void generateBadge(Event e) {
+  setBadgeName('Anne Bonney');
+}
+
+void setBadgeName(String newName) {
+  querySelector('#badgeName').text = newName;
+}