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

samples/swarm/swarm_ui_lib/touch/Scroller.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.
 
 /**
  * Implementation of a custom scrolling behavior.
  * This behavior overrides native scrolling for an area. This area can be a
  * single defined part of a page, the entire page, or several different parts
  * of a page.
  *
@@ skipping 126 matching lines @@
   Scroller(Element scrollableElem, [this.verticalEnabled = false,
            this.horizontalEnabled = false,
            momentumEnabled = true,
            lookupContentSizeDelegate = null,
            num defaultDecelerationFactor = 1,
            int scrollTechnique = null, bool capture = false])
       : _momentumEnabled = momentumEnabled,
         _lookupContentSizeDelegate = lookupContentSizeDelegate,
         _element = scrollableElem,
         _frame = scrollableElem.parent,
-        _scrollTechnique = scrollTechnique !== null
+        _scrollTechnique = scrollTechnique != null
             ? scrollTechnique : ScrollerScrollTechnique.TRANSFORM_3D,
         _minPoint = new Coordinate(0, 0),
         _maxPoint = new Coordinate(0, 0),
         _maxOffset = new Coordinate(0, 0),
         _minOffset = new Coordinate(0, 0),
         _contentOffset = new Coordinate(0, 0) {
     _touchHandler = new TouchHandler(this, scrollableElem.parent);
     _momentum = new Momentum(this, defaultDecelerationFactor);
 
     Element parentElem = scrollableElem.parent;
@@ skipping 75 matching lines @@
     if (_scrollTechnique == ScrollerScrollTechnique.RELATIVE_POSITIONING) {
       _element.computedStyle.then((CSSStyleDeclaration style) {
         assert(style.position != "static");
       });
     }
 
     _initLayer();
   }
 
   EventListenerList get onScrollerStart {
-    if (_onScrollerStart === null) {
+    if (_onScrollerStart == null) {
       _onScrollerStart = new SimpleEventListenerList();
     }
     return _onScrollerStart;
   }
 
   EventListenerList get onScrollerEnd {
-    if (_onScrollerEnd === null) {
+    if (_onScrollerEnd == null) {
       _onScrollerEnd = new SimpleEventListenerList();
     }
     return _onScrollerEnd;
   }
 
   EventListenerList get onScrollerDragEnd {
-    if (_onScrollerDragEnd === null) {
+    if (_onScrollerDragEnd == null) {
       _onScrollerDragEnd = new SimpleEventListenerList();
     }
     return _onScrollerDragEnd;
   }
 
   EventListenerList get onContentMoved {
-    if (_onContentMoved === null) {
+    if (_onContentMoved == null) {
       _onContentMoved = new SimpleEventListenerList();
     }
     return _onContentMoved;
   }
 
   EventListenerList get onDecelStart {
-    if (_onDecelStart === null) {
+    if (_onDecelStart == null) {
       _onDecelStart = new SimpleEventListenerList();
     }
     return _onDecelStart;
   }
 
 
   /**
    * Add a scroll listener. This allows other classes to subscribe to scroll
    * notifications from this scroller.
    */
   void addScrollListener(ScrollListener listener) {
-    if (_scrollWatcher === null) {
+    if (_scrollWatcher == null) {
       _scrollWatcher = new ScrollWatcher(this);
       _scrollWatcher.initialize();
     }
     _scrollWatcher.addListener(listener);
   }
 
   /**
    * Adjust the new calculated scroll position based on the minimum allowed
    * position and returns the adjusted scroll value.
    */
   num _adjustValue(num newPosition, num minPosition,
                       num maxPosition) {
     assert(minPosition <= maxPosition);
 
     if (newPosition < minPosition) {
       newPosition -= (newPosition - minPosition) / 2;
     } else {
       if (newPosition > maxPosition) {
         newPosition -= (newPosition - maxPosition) / 2;
       }
     }
     return newPosition;
   }
 
   /**
    * Coordinate we would end up at if we did nothing.
    */
   Coordinate get currentTarget {
     Coordinate end = _momentum.destination;
-    if (end === null) {
+    if (end == null) {
       end = _contentOffset;
     }
     return end;
   }
 
   Coordinate get contentOffset => _contentOffset;
 
   /**
    * Animate the position of the scroller to the specified [x], [y] coordinates
    * by applying the throw gesture with the correct velocity to end at that
@@ skipping 61 matching lines @@
   Element getElement() => _element;
   Element getFrame() => _frame;
   num getHorizontalOffset() => _contentOffset.x;
 
   /**
    * [x] Value to use as reference for percent measurement. If
    *      none is provided then the content's current x offset will be used.
    * Returns the percent of the page scrolled horizontally.
    */
   num getHorizontalScrollPercent([num x = null]) {
-    x = x !== null ? x : _contentOffset.x;
+    x = x != null ? x : _contentOffset.x;
     return (x - _minPoint.x) / (_maxPoint.x - _minPoint.x);
   }
 
   num getMaxPointY()=> _maxPoint.y;
   num getMinPointY() => _minPoint.y;
   Momentum get momentum => _momentum;
 
   /**
    * Provide access to the touch handler that the scroller created to manage
    * touch events.
    */
   TouchHandler getTouchHandler() => _touchHandler;
   num getVerticalOffset() => _contentOffset.y;
 
   /**
    * [y] value is used as reference for percent measurement. If
    * none is provided then the content's current y offset will be used.
    */
   num getVerticalScrollPercent([num y = null]) {
-    y = y !== null ? y : _contentOffset.y;
+    y = y != null ? y : _contentOffset.y;
     return (y - _minPoint.y) / Math.max(1, _maxPoint.y - _minPoint.y);
   }
 
   /**
    * Initialize the dom elements necessary for the scrolling to work.
    */
   void _initLayer() {
     // The scrollable node provided to Scroller must be a direct child
     // of the scrollable frame.
     // TODO(jacobr): Figure out why this is failing on dartium.
@@ skipping 109 matching lines @@
     _minOffset.y = 0;
     reconfigure(() => _setContentOffset(_maxPoint.x, _maxPoint.y));
   }
 
   /**
    * Recalculate dimensions of the frame and the content. Adjust the minPoint
    * and maxPoint allowed for scrolling.
    */
   void _resize(Callback callback) {
     window.requestLayoutFrame(() {
-      if (_lookupContentSizeDelegate !== null) {
+      if (_lookupContentSizeDelegate != null) {
         _contentSize = _lookupContentSizeDelegate();
       } else {
         _contentSize = new Size(_element.scrollWidth, _element.scrollHeight);
       }
 
       _scrollSize = new Size(_frame.offsetWidth,
                              _frame.offsetHeight);
       Size adjusted = _getAdjustedContentSize();
       _maxPoint = new Coordinate(-_maxOffset.x, -_maxOffset.y);
       _minPoint = new Coordinate(
@@ skipping 157 matching lines @@
     for (EventListener listener in _listeners) {
       listener(evt);
     }
   }
 }
 
 class ScrollerScrollTechnique {
   static const TRANSFORM_3D = 1;
   static const RELATIVE_POSITIONING = 2;
 }