From e1f477ad8cbfdac2d9a38721f400c76091deae78 Mon Sep 17 00:00:00 2001
From: Marc Jansen <jansen@terrestris.de>
Date: Tue, 29 Sep 2015 15:20:51 +0200
Subject: [PATCH] Remove goog.isNull in source classes

---
 src/ol/source/bingmapssource.js       |  2 +-
 src/ol/source/imagecanvassource.js    |  4 +--
 src/ol/source/imagemapguidesource.js  |  2 +-
 src/ol/source/imagesource.js          |  4 +--
 src/ol/source/imagevectorsource.js    |  4 +--
 src/ol/source/imagewmssource.js       |  2 +-
 src/ol/source/rastersource.js         |  2 +-
 src/ol/source/tilearcgisrestsource.js |  2 +-
 src/ol/source/tiledebugsource.js      |  2 +-
 src/ol/source/tileimagesource.js      |  2 +-
 src/ol/source/tilejsonsource.js       |  3 +-
 src/ol/source/tilesource.js           |  4 +--
 src/ol/source/tileutfgridsource.js    |  4 +--
 src/ol/source/tilevectorsource.js     |  9 +++---
 src/ol/source/tilewmssource.js        |  4 +--
 src/ol/source/vectorsource.js         | 40 +++++++++++++--------------
 src/ol/source/wmtssource.js           | 14 ++++------
 src/ol/source/zoomifysource.js        |  2 +-
 18 files changed, 51 insertions(+), 55 deletions(-)

diff --git a/src/ol/source/bingmapssource.js b/src/ol/source/bingmapssource.js
index 90a827e1b1..998d439442 100644
--- a/src/ol/source/bingmapssource.js
+++ b/src/ol/source/bingmapssource.js
@@ -130,7 +130,7 @@ ol.source.BingMaps.prototype.handleImageryMetadataResponse =
               goog.asserts.assert(ol.proj.equivalent(
                   projection, sourceProjection),
                   'projections are equivalent');
-              if (goog.isNull(tileCoord)) {
+              if (!tileCoord) {
                 return undefined;
               } else {
                 ol.tilecoord.createOrUpdate(tileCoord[0], tileCoord[1],
diff --git a/src/ol/source/imagecanvassource.js b/src/ol/source/imagecanvassource.js
index ba8e8a15f4..8532e8b313 100644
--- a/src/ol/source/imagecanvassource.js
+++ b/src/ol/source/imagecanvassource.js
@@ -64,7 +64,7 @@ ol.source.ImageCanvas.prototype.getImage =
   resolution = this.findNearestResolution(resolution);
 
   var canvas = this.canvas_;
-  if (!goog.isNull(canvas) &&
+  if (canvas &&
       this.renderedRevision_ == this.getRevision() &&
       canvas.getResolution() == resolution &&
       canvas.getPixelRatio() == pixelRatio &&
@@ -80,7 +80,7 @@ ol.source.ImageCanvas.prototype.getImage =
 
   var canvasElement = this.canvasFunction_(
       extent, resolution, pixelRatio, size, projection);
-  if (!goog.isNull(canvasElement)) {
+  if (canvasElement) {
     canvas = new ol.ImageCanvas(extent, resolution, pixelRatio,
         this.getAttributions(), canvasElement);
   }
diff --git a/src/ol/source/imagemapguidesource.js b/src/ol/source/imagemapguidesource.js
index 899d8663d0..031becffb9 100644
--- a/src/ol/source/imagemapguidesource.js
+++ b/src/ol/source/imagemapguidesource.js
@@ -132,7 +132,7 @@ ol.source.ImageMapGuide.prototype.getImage =
   pixelRatio = this.hidpi_ ? pixelRatio : 1;
 
   var image = this.image_;
-  if (!goog.isNull(image) &&
+  if (image &&
       this.renderedRevision_ == this.getRevision() &&
       image.getResolution() == resolution &&
       image.getPixelRatio() == pixelRatio &&
diff --git a/src/ol/source/imagesource.js b/src/ol/source/imagesource.js
index 2865fb6511..3bd9afe517 100644
--- a/src/ol/source/imagesource.js
+++ b/src/ol/source/imagesource.js
@@ -50,7 +50,7 @@ ol.source.Image = function(options) {
    */
   this.resolutions_ = options.resolutions !== undefined ?
       options.resolutions : null;
-  goog.asserts.assert(goog.isNull(this.resolutions_) ||
+  goog.asserts.assert(!this.resolutions_ ||
       goog.array.isSorted(this.resolutions_,
           function(a, b) {
             return b - a;
@@ -75,7 +75,7 @@ ol.source.Image.prototype.getResolutions = function() {
  */
 ol.source.Image.prototype.findNearestResolution =
     function(resolution) {
-  if (!goog.isNull(this.resolutions_)) {
+  if (this.resolutions_) {
     var idx = ol.array.linearFindNearest(this.resolutions_, resolution, 0);
     resolution = this.resolutions_[idx];
   }
diff --git a/src/ol/source/imagevectorsource.js b/src/ol/source/imagevectorsource.js
index 4e8dc606f0..c940996abd 100644
--- a/src/ol/source/imagevectorsource.js
+++ b/src/ol/source/imagevectorsource.js
@@ -154,7 +154,7 @@ ol.source.ImageVector.prototype.canvasFunctionInternal_ =
  */
 ol.source.ImageVector.prototype.forEachFeatureAtCoordinate = function(
     coordinate, resolution, rotation, skippedFeatureUids, callback) {
-  if (goog.isNull(this.replayGroup_)) {
+  if (!this.replayGroup_) {
     return undefined;
   } else {
     /** @type {Object.<string, boolean>} */
@@ -292,7 +292,7 @@ ol.source.ImageVector.prototype.renderFeature_ =
  */
 ol.source.ImageVector.prototype.setStyle = function(style) {
   this.style_ = style !== undefined ? style : ol.style.defaultStyleFunction;
-  this.styleFunction_ = goog.isNull(style) ?
+  this.styleFunction_ = !style ?
       undefined : ol.style.createStyleFunction(this.style_);
   this.changed();
 };
diff --git a/src/ol/source/imagewmssource.js b/src/ol/source/imagewmssource.js
index c7e25299d0..e9b49b95fd 100644
--- a/src/ol/source/imagewmssource.js
+++ b/src/ol/source/imagewmssource.js
@@ -223,7 +223,7 @@ ol.source.ImageWMS.prototype.getImage =
   extent[3] = centerY + imageResolution * height / 2;
 
   var image = this.image_;
-  if (!goog.isNull(image) &&
+  if (image &&
       this.renderedRevision_ == this.getRevision() &&
       image.getResolution() == resolution &&
       image.getPixelRatio() == pixelRatio &&
diff --git a/src/ol/source/rastersource.js b/src/ol/source/rastersource.js
index bc37f0305c..8121573a69 100644
--- a/src/ol/source/rastersource.js
+++ b/src/ol/source/rastersource.js
@@ -319,7 +319,7 @@ ol.source.Raster.prototype.onWorkerComplete_ =
     callback(err);
     return;
   }
-  if (goog.isNull(output)) {
+  if (!output) {
     // job aborted
     return;
   }
diff --git a/src/ol/source/tilearcgisrestsource.js b/src/ol/source/tilearcgisrestsource.js
index 97b031056c..3a105fe646 100644
--- a/src/ol/source/tilearcgisrestsource.js
+++ b/src/ol/source/tilearcgisrestsource.js
@@ -200,7 +200,7 @@ ol.source.TileArcGISRest.prototype.tileUrlFunction_ =
     function(tileCoord, pixelRatio, projection) {
 
   var tileGrid = this.getTileGrid();
-  if (goog.isNull(tileGrid)) {
+  if (!tileGrid) {
     tileGrid = this.getTileGridForProjection(projection);
   }
 
diff --git a/src/ol/source/tiledebugsource.js b/src/ol/source/tiledebugsource.js
index 41aed6df4a..3bfd917b34 100644
--- a/src/ol/source/tiledebugsource.js
+++ b/src/ol/source/tiledebugsource.js
@@ -110,7 +110,7 @@ ol.source.TileDebug.prototype.getTile = function(z, x, y) {
     var tileSize = ol.size.toSize(this.tileGrid.getTileSize(z));
     var tileCoord = [z, x, y];
     var textTileCoord = this.getTileCoordForTileUrlFunction(tileCoord);
-    var text = goog.isNull(textTileCoord) ? '' : ol.tilecoord.toString(
+    var text = !textTileCoord ? '' : ol.tilecoord.toString(
         this.getTileCoordForTileUrlFunction(textTileCoord));
     var tile = new ol.DebugTile_(tileCoord, tileSize, text);
     this.tileCache.set(tileCoordKey, tile);
diff --git a/src/ol/source/tileimagesource.js b/src/ol/source/tileimagesource.js
index 1fddb16652..fa92f0671d 100644
--- a/src/ol/source/tileimagesource.js
+++ b/src/ol/source/tileimagesource.js
@@ -95,7 +95,7 @@ ol.source.TileImage.prototype.getTile =
     var tileCoord = [z, x, y];
     var urlTileCoord = this.getTileCoordForTileUrlFunction(
         tileCoord, projection);
-    var tileUrl = goog.isNull(urlTileCoord) ? undefined :
+    var tileUrl = !urlTileCoord ? undefined :
         this.tileUrlFunction(urlTileCoord, pixelRatio, projection);
     var tile = new this.tileClass(
         tileCoord,
diff --git a/src/ol/source/tilejsonsource.js b/src/ol/source/tilejsonsource.js
index 2730c7be2b..e1c3f854fc 100644
--- a/src/ol/source/tilejsonsource.js
+++ b/src/ol/source/tilejsonsource.js
@@ -78,8 +78,7 @@ ol.source.TileJSON.prototype.handleTileJSONResponse = function(tileJSON) {
   this.tileUrlFunction =
       ol.TileUrlFunction.createFromTemplates(tileJSON.tiles, tileGrid);
 
-  if (tileJSON.attribution !== undefined &&
-      goog.isNull(this.getAttributions())) {
+  if (tileJSON.attribution !== undefined && !this.getAttributions()) {
     var attributionExtent = extent !== undefined ?
         extent : epsg4326Projection.getExtent();
     /** @type {Object.<string, Array.<ol.TileRange>>} */
diff --git a/src/ol/source/tilesource.js b/src/ol/source/tilesource.js
index b9cb312290..111fb6cf18 100644
--- a/src/ol/source/tilesource.js
+++ b/src/ol/source/tilesource.js
@@ -195,7 +195,7 @@ ol.source.Tile.prototype.getTileGrid = function() {
  * @return {ol.tilegrid.TileGrid} Tile grid.
  */
 ol.source.Tile.prototype.getTileGridForProjection = function(projection) {
-  if (goog.isNull(this.tileGrid)) {
+  if (!this.tileGrid) {
     return ol.tilegrid.getForProjection(projection);
   } else {
     return this.tileGrid;
@@ -231,7 +231,7 @@ ol.source.Tile.prototype.getTileCoordForTileUrlFunction =
   var projection = opt_projection !== undefined ?
       opt_projection : this.getProjection();
   var tileGrid = this.getTileGridForProjection(projection);
-  goog.asserts.assert(!goog.isNull(tileGrid), 'tile grid needed');
+  goog.asserts.assert(tileGrid, 'tile grid needed');
   if (this.getWrapX() && projection.isGlobal()) {
     tileCoord = ol.tilecoord.wrapX(tileCoord, tileGrid, projection);
   }
diff --git a/src/ol/source/tileutfgridsource.js b/src/ol/source/tileutfgridsource.js
index a25e568cc7..8862353677 100644
--- a/src/ol/source/tileutfgridsource.js
+++ b/src/ol/source/tileutfgridsource.js
@@ -81,7 +81,7 @@ ol.source.TileUTFGrid.prototype.getTemplate = function() {
  */
 ol.source.TileUTFGrid.prototype.forDataAtCoordinateAndResolution = function(
     coordinate, resolution, callback, opt_this, opt_request) {
-  if (!goog.isNull(this.tileGrid)) {
+  if (this.tileGrid) {
     var tileCoord = this.tileGrid.getTileCoordForCoordAndResolution(
         coordinate, resolution);
     var tile = /** @type {!ol.source.TileUTFGridTile_} */(this.getTile(
@@ -269,7 +269,7 @@ ol.source.TileUTFGridTile_.prototype.getImage = function(opt_context) {
  * @return {Object}
  */
 ol.source.TileUTFGridTile_.prototype.getData = function(coordinate) {
-  if (goog.isNull(this.grid_) || goog.isNull(this.keys_) || !this.data_) {
+  if (!this.grid_ || !this.keys_ || !this.data_) {
     return null;
   }
   var xRelative = (coordinate[0] - this.extent_[0]) /
diff --git a/src/ol/source/tilevectorsource.js b/src/ol/source/tilevectorsource.js
index d13778c07c..902dafb021 100644
--- a/src/ol/source/tilevectorsource.js
+++ b/src/ol/source/tilevectorsource.js
@@ -57,8 +57,7 @@ ol.source.TileVector = function(options) {
   this.tileLoadFunction_ = options.tileLoadFunction !== undefined ?
       options.tileLoadFunction : null;
 
-  goog.asserts.assert(!goog.isNull(this.format_) ||
-      !goog.isNull(this.tileLoadFunction_),
+  goog.asserts.assert(this.format_ || this.tileLoadFunction_,
       'Either format or tileLoadFunction are required');
 
   /**
@@ -252,7 +251,7 @@ ol.source.TileVector.prototype.getFeaturesInExtent = goog.abstractMethod;
 ol.source.TileVector.prototype.getTileCoordForTileUrlFunction =
     function(tileCoord, projection) {
   var tileGrid = this.tileGrid_;
-  goog.asserts.assert(!goog.isNull(tileGrid), 'tile grid needed');
+  goog.asserts.assert(tileGrid, 'tile grid needed');
   if (this.getWrapX() && projection.isGlobal()) {
     tileCoord = ol.tilecoord.wrapX(tileCoord, tileGrid, projection);
   }
@@ -302,12 +301,12 @@ ol.source.TileVector.prototype.loadFeatures =
         tileCoord[2] = y;
         var urlTileCoord = this.getTileCoordForTileUrlFunction(
             tileCoord, projection);
-        var url = goog.isNull(urlTileCoord) ? undefined :
+        var url = !urlTileCoord ? undefined :
             tileUrlFunction(urlTileCoord, 1, projection);
         if (url !== undefined) {
           tiles[tileKey] = [];
           var tileSuccess = goog.partial(success, tileKey);
-          if (!goog.isNull(this.tileLoadFunction_)) {
+          if (this.tileLoadFunction_) {
             this.tileLoadFunction_(url, goog.bind(tileSuccess, this));
           } else {
             var loader = ol.featureloader.loadFeaturesXhr(url,
diff --git a/src/ol/source/tilewmssource.js b/src/ol/source/tilewmssource.js
index 5f015cd07d..e3ad0ed0d3 100644
--- a/src/ol/source/tilewmssource.js
+++ b/src/ol/source/tilewmssource.js
@@ -135,7 +135,7 @@ ol.source.TileWMS.prototype.getGetFeatureInfoUrl =
   var projectionObj = ol.proj.get(projection);
 
   var tileGrid = this.getTileGrid();
-  if (goog.isNull(tileGrid)) {
+  if (!tileGrid) {
     tileGrid = this.getTileGridForProjection(projectionObj);
   }
 
@@ -365,7 +365,7 @@ ol.source.TileWMS.prototype.tileUrlFunction_ =
     function(tileCoord, pixelRatio, projection) {
 
   var tileGrid = this.getTileGrid();
-  if (goog.isNull(tileGrid)) {
+  if (!tileGrid) {
     tileGrid = this.getTileGridForProjection(projection);
   }
 
diff --git a/src/ol/source/vectorsource.js b/src/ol/source/vectorsource.js
index c562df0eb7..d36696c86f 100644
--- a/src/ol/source/vectorsource.js
+++ b/src/ol/source/vectorsource.js
@@ -206,7 +206,7 @@ ol.source.Vector.prototype.addFeatureInternal = function(feature) {
   var geometry = feature.getGeometry();
   if (geometry) {
     var extent = geometry.getExtent();
-    if (!goog.isNull(this.featuresRtree_)) {
+    if (this.featuresRtree_) {
       this.featuresRtree_.insert(extent, feature);
     }
   } else {
@@ -307,7 +307,7 @@ ol.source.Vector.prototype.addFeaturesInternal = function(features) {
       this.nullGeometryFeatures_[featureKey] = feature;
     }
   }
-  if (!goog.isNull(this.featuresRtree_)) {
+  if (this.featuresRtree_) {
     this.featuresRtree_.load(extents, geometryFeatures);
   }
 
@@ -323,7 +323,7 @@ ol.source.Vector.prototype.addFeaturesInternal = function(features) {
  * @private
  */
 ol.source.Vector.prototype.bindFeaturesCollection_ = function(collection) {
-  goog.asserts.assert(goog.isNull(this.featuresCollection_),
+  goog.asserts.assert(!this.featuresCollection_,
       'bindFeaturesCollection can only be called once');
   var modifyingCollection = false;
   goog.events.listen(this, ol.source.VectorEventType.ADDFEATURE,
@@ -377,19 +377,19 @@ ol.source.Vector.prototype.clear = function(opt_fast) {
       var keys = this.featureChangeKeys_[featureId];
       keys.forEach(goog.events.unlistenByKey);
     }
-    if (goog.isNull(this.featuresCollection_)) {
+    if (!this.featuresCollection_) {
       this.featureChangeKeys_ = {};
       this.idIndex_ = {};
       this.undefIdIndex_ = {};
     }
   } else {
     var rmFeatureInternal = this.removeFeatureInternal;
-    if (!goog.isNull(this.featuresRtree_)) {
+    if (this.featuresRtree_) {
       this.featuresRtree_.forEach(rmFeatureInternal, this);
       goog.object.forEach(this.nullGeometryFeatures_, rmFeatureInternal, this);
     }
   }
-  if (!goog.isNull(this.featuresCollection_)) {
+  if (this.featuresCollection_) {
     this.featuresCollection_.clear();
   }
   goog.asserts.assert(goog.object.isEmpty(this.featureChangeKeys_),
@@ -399,7 +399,7 @@ ol.source.Vector.prototype.clear = function(opt_fast) {
   goog.asserts.assert(goog.object.isEmpty(this.undefIdIndex_),
       'undefIdIndex is an empty object now');
 
-  if (!goog.isNull(this.featuresRtree_)) {
+  if (this.featuresRtree_) {
     this.featuresRtree_.clear();
   }
   this.loadedExtentsRtree_.clear();
@@ -424,9 +424,9 @@ ol.source.Vector.prototype.clear = function(opt_fast) {
  * @api stable
  */
 ol.source.Vector.prototype.forEachFeature = function(callback, opt_this) {
-  if (!goog.isNull(this.featuresRtree_)) {
+  if (this.featuresRtree_) {
     return this.featuresRtree_.forEach(callback, opt_this);
-  } else if (!goog.isNull(this.featuresCollection_)) {
+  } else if (this.featuresCollection_) {
     return this.featuresCollection_.forEach(callback, opt_this);
   }
 };
@@ -483,9 +483,9 @@ ol.source.Vector.prototype.forEachFeatureAtCoordinateDirect =
  */
 ol.source.Vector.prototype.forEachFeatureInExtent =
     function(extent, callback, opt_this) {
-  if (!goog.isNull(this.featuresRtree_)) {
+  if (this.featuresRtree_) {
     return this.featuresRtree_.forEachInExtent(extent, callback, opt_this);
-  } else if (!goog.isNull(this.featuresCollection_)) {
+  } else if (this.featuresCollection_) {
     return this.featuresCollection_.forEach(callback, opt_this);
   }
 };
@@ -563,9 +563,9 @@ ol.source.Vector.prototype.getFeaturesCollection = function() {
  */
 ol.source.Vector.prototype.getFeatures = function() {
   var features;
-  if (!goog.isNull(this.featuresCollection_)) {
+  if (this.featuresCollection_) {
     features = this.featuresCollection_.getArray();
-  } else if (!goog.isNull(this.featuresRtree_)) {
+  } else if (this.featuresRtree_) {
     features = this.featuresRtree_.getAll();
     if (!goog.object.isEmpty(this.nullGeometryFeatures_)) {
       goog.array.extend(
@@ -605,7 +605,7 @@ ol.source.Vector.prototype.getFeaturesAtCoordinate = function(coordinate) {
  * @api
  */
 ol.source.Vector.prototype.getFeaturesInExtent = function(extent) {
-  goog.asserts.assert(!goog.isNull(this.featuresRtree_),
+  goog.asserts.assert(this.featuresRtree_,
       'getFeaturesInExtent does not work when useSpatialIndex is set to false');
   return this.featuresRtree_.getInExtent(extent);
 };
@@ -635,7 +635,7 @@ ol.source.Vector.prototype.getClosestFeatureToCoordinate =
   var closestPoint = [NaN, NaN];
   var minSquaredDistance = Infinity;
   var extent = [-Infinity, -Infinity, Infinity, Infinity];
-  goog.asserts.assert(!goog.isNull(this.featuresRtree_),
+  goog.asserts.assert(this.featuresRtree_,
       'getClosestFeatureToCoordinate does not work with useSpatialIndex set ' +
       'to false');
   this.featuresRtree_.forEachInExtent(extent,
@@ -675,7 +675,7 @@ ol.source.Vector.prototype.getClosestFeatureToCoordinate =
  * @api stable
  */
 ol.source.Vector.prototype.getExtent = function() {
-  goog.asserts.assert(!goog.isNull(this.featuresRtree_),
+  goog.asserts.assert(this.featuresRtree_,
       'getExtent does not work when useSpatialIndex is set to false');
   return this.featuresRtree_.getExtent();
 };
@@ -706,7 +706,7 @@ ol.source.Vector.prototype.handleFeatureChange_ = function(event) {
   var geometry = feature.getGeometry();
   if (!geometry) {
     if (!(featureKey in this.nullGeometryFeatures_)) {
-      if (!goog.isNull(this.featuresRtree_)) {
+      if (this.featuresRtree_) {
         this.featuresRtree_.remove(feature);
       }
       this.nullGeometryFeatures_[featureKey] = feature;
@@ -715,11 +715,11 @@ ol.source.Vector.prototype.handleFeatureChange_ = function(event) {
     var extent = geometry.getExtent();
     if (featureKey in this.nullGeometryFeatures_) {
       delete this.nullGeometryFeatures_[featureKey];
-      if (!goog.isNull(this.featuresRtree_)) {
+      if (this.featuresRtree_) {
         this.featuresRtree_.insert(extent, feature);
       }
     } else {
-      if (!goog.isNull(this.featuresRtree_)) {
+      if (this.featuresRtree_) {
         this.featuresRtree_.update(extent, feature);
       }
     }
@@ -805,7 +805,7 @@ ol.source.Vector.prototype.removeFeature = function(feature) {
   if (featureKey in this.nullGeometryFeatures_) {
     delete this.nullGeometryFeatures_[featureKey];
   } else {
-    if (!goog.isNull(this.featuresRtree_)) {
+    if (this.featuresRtree_) {
       this.featuresRtree_.remove(feature);
     }
   }
diff --git a/src/ol/source/wmtssource.js b/src/ol/source/wmtssource.js
index 4bb1dfdeb0..05583563cf 100644
--- a/src/ol/source/wmtssource.js
+++ b/src/ol/source/wmtssource.js
@@ -154,7 +154,7 @@ ol.source.WMTS = function(options) {
          * @return {string|undefined} Tile URL.
          */
         function(tileCoord, pixelRatio, projection) {
-          if (goog.isNull(tileCoord)) {
+          if (!tileCoord) {
             return undefined;
           } else {
             var localContext = {
@@ -341,15 +341,14 @@ ol.source.WMTS.optionsFromCapabilities = function(wmtsCap, config) {
   /* jshint -W069 */
 
   // TODO: add support for TileMatrixLimits
-  goog.asserts.assert(!goog.isNull(config['layer']),
+  goog.asserts.assert(config['layer'],
       'config "layer" must not be null');
 
   var layers = wmtsCap['Contents']['Layer'];
   var l = goog.array.find(layers, function(elt, index, array) {
     return elt['Identifier'] == config['layer'];
   });
-  goog.asserts.assert(!goog.isNull(l),
-      'found a matching layer in Contents/Layer');
+  goog.asserts.assert(l, 'found a matching layer in Contents/Layer');
 
   goog.asserts.assert(l['TileMatrixSetLink'].length > 0,
       'layer has TileMatrixSetLink');
@@ -381,8 +380,7 @@ ol.source.WMTS.optionsFromCapabilities = function(wmtsCap, config) {
   matrixSet = /** @type {string} */
       (l['TileMatrixSetLink'][idx]['TileMatrixSet']);
 
-  goog.asserts.assert(!goog.isNull(matrixSet),
-      'TileMatrixSet must not be null');
+  goog.asserts.assert(matrixSet, 'TileMatrixSet must not be null');
 
   var format = /** @type {string} */ (l['Format'][0]);
   if ('format' in config) {
@@ -420,7 +418,7 @@ ol.source.WMTS.optionsFromCapabilities = function(wmtsCap, config) {
   var matrixSetObj = goog.array.find(matrixSets, function(elt, index, array) {
     return elt['Identifier'] == matrixSet;
   });
-  goog.asserts.assert(!goog.isNull(matrixSetObj),
+  goog.asserts.assert(matrixSetObj,
       'found matrixSet in Contents/TileMatrixSet');
 
   var projection;
@@ -440,7 +438,7 @@ ol.source.WMTS.optionsFromCapabilities = function(wmtsCap, config) {
     extent = ol.proj.transformExtent(
         wgs84BoundingBox, 'EPSG:4326', projection);
     var projectionExtent = projection.getExtent();
-    if (!goog.isNull(projectionExtent)) {
+    if (projectionExtent) {
       // If possible, do a sanity check on the extent - it should never be
       // bigger than the validity extent of the projection of a matrix set.
       if (!ol.extent.containsExtent(projectionExtent, extent)) {
diff --git a/src/ol/source/zoomifysource.js b/src/ol/source/zoomifysource.js
index ca2166d101..f9533a74b0 100644
--- a/src/ol/source/zoomifysource.js
+++ b/src/ol/source/zoomifysource.js
@@ -104,7 +104,7 @@ ol.source.Zoomify = function(opt_options) {
    * @return {string|undefined} Tile URL.
    */
   function tileUrlFunction(tileCoord, pixelRatio, projection) {
-    if (goog.isNull(tileCoord)) {
+    if (!tileCoord) {
       return undefined;
     } else {
       var tileCoordZ = tileCoord[0];