a === b -> identical(a, b)

samples/swarm/swarm_ui_lib/observable/observable.dart

 // Copyright (c) 2011, 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.
 
 library observable;
 
 import 'dart:coreimpl';
 
 part 'ChangeEvent.dart';
 part 'EventBatch.dart';
@@ skipping 197 matching lines @@
       recordListRemove(index, found);
     }
     return found;
   }
 
   int indexOf(T element, [int start = 0]) {
     return _internal.indexOf(element, start);
   }
 
   int lastIndexOf(T element, [int start = null]) {
-    if (start === null) start = length - 1;
+    if (start == null) start = length - 1;
     return _internal.lastIndexOf(element, start);
   }
 
   bool removeFirstElement(T element) {
     // the removeAt above will record the event.
     return (removeAt(indexOf(element, 0)) != null);
   }
 
   int removeAllElements(T element) {
     int count = 0;
@@ skipping 49 matching lines @@
 // "new ObservableValue<DataType>(myValue)".
 /** A wrapper around a single value whose change can be observed. */
 class ObservableValue<T> extends AbstractObservable {
   ObservableValue(T value, [Observable parent = null])
     : super(parent), _value = value;
 
   T get value => _value;
 
   void set value(T newValue) {
     // Only fire on an actual change.
-    // TODO(terry): An object identity test === is needed.  Each DataSource has
-    //              its own operator == which does a value compare.  Which
-    //              equality check should be done?
-    if (newValue !== _value) {
+    if (!identical(newValue, _value)) {
       final oldValue = _value;
       _value = newValue;
       recordPropertyUpdate("value", newValue, oldValue);
     }
   }
 
   T _value;
 }