Open your javascript Console and either:
 e.setAttribute('hello','world');
 o.foo = 'bar';
 a.push('yep');
		
  final GQuery g =  $("div");
  final Properties o = $$();
  final JsArrayString a = JsArray.createArray().cast();
  public void onModuleLoad() {
    $(window).prop("e", g.get(0)).prop("o", o).prop("a", a);
    g.as(Observe.Observe).mutation(
             Observe.createMutationInit()
                    .attributes(true)
                    .characterData(true)
                    .childList(true)
                    .subtree(true),
             new MutationListener() {
      public void onMutation(List<MutationRecord> mutations) {
        for (MutationRecord r: mutations) {
          console.log("M - > ", r.getDataImpl());
        }
      }
    });
    Observe.observe(o, new ObserveListener() {
      public void onChange(List<ChangeRecord> changes) {
        for(ChangeRecord r : changes) {
          console.log("O -> ", r.getDataImpl());
        }
      }
    });
    Observe.observe(a, new ObserveListener() {
      public void onChange(List<ChangeRecord> changes) {
        for(ChangeRecord r : changes) {
          console.log("A -> ", r.getDataImpl());
        }
      }
    });
  }