diff --git a/src/ol/animation.js b/src/ol/animation.js
index 624732f0dc..3d67b58af8 100644
--- a/src/ol/animation.js
+++ b/src/ol/animation.js
@@ -17,22 +17,27 @@ ol.animation.bounce = function(options) {
   var duration = goog.isDef(options.duration) ? options.duration : 1000;
   var easing = goog.isDef(options.easing) ?
       options.easing : ol.easing.upAndDown;
-  return function(map, frameState) {
-    if (frameState.time < start) {
-      frameState.animate = true;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else if (frameState.time < start + duration) {
-      var delta = easing((frameState.time - start) / duration);
-      var deltaResolution = resolution - frameState.view2DState.resolution;
-      frameState.animate = true;
-      frameState.view2DState.resolution += delta * deltaResolution;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else {
-      return false;
-    }
-  };
+  return (
+      /**
+       * @param {ol.Map} map Map.
+       * @param {?ol.FrameState} frameState Frame state.
+       */
+      function(map, frameState) {
+        if (frameState.time < start) {
+          frameState.animate = true;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else if (frameState.time < start + duration) {
+          var delta = easing((frameState.time - start) / duration);
+          var deltaResolution = resolution - frameState.view2DState.resolution;
+          frameState.animate = true;
+          frameState.view2DState.resolution += delta * deltaResolution;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else {
+          return false;
+        }
+      });
 };
 
 
@@ -48,24 +53,29 @@ ol.animation.pan = function(options) {
   var duration = goog.isDef(options.duration) ? options.duration : 1000;
   var easing = goog.isDef(options.easing) ?
       options.easing : ol.easing.inAndOut;
-  return function(map, frameState) {
-    if (frameState.time < start) {
-      frameState.animate = true;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else if (frameState.time < start + duration) {
-      var delta = 1 - easing((frameState.time - start) / duration);
-      var deltaX = sourceX - frameState.view2DState.center[0];
-      var deltaY = sourceY - frameState.view2DState.center[1];
-      frameState.animate = true;
-      frameState.view2DState.center[0] += delta * deltaX;
-      frameState.view2DState.center[1] += delta * deltaY;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else {
-      return false;
-    }
-  };
+  return (
+      /**
+       * @param {ol.Map} map Map.
+       * @param {?ol.FrameState} frameState Frame state.
+       */
+      function(map, frameState) {
+        if (frameState.time < start) {
+          frameState.animate = true;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else if (frameState.time < start + duration) {
+          var delta = 1 - easing((frameState.time - start) / duration);
+          var deltaX = sourceX - frameState.view2DState.center[0];
+          var deltaY = sourceY - frameState.view2DState.center[1];
+          frameState.animate = true;
+          frameState.view2DState.center[0] += delta * deltaX;
+          frameState.view2DState.center[1] += delta * deltaY;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else {
+          return false;
+        }
+      });
 };
 
 
@@ -80,23 +90,28 @@ ol.animation.rotate = function(options) {
   var easing = goog.isDef(options.easing) ?
       options.easing : ol.easing.inAndOut;
 
-  return function(map, frameState) {
-    if (frameState.time < start) {
-      frameState.animate = true;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else if (frameState.time < start + duration) {
-      var delta = 1 - easing((frameState.time - start) / duration);
-      var deltaRotation =
-          sourceRotation - frameState.view2DState.rotation;
-      frameState.animate = true;
-      frameState.view2DState.rotation += delta * deltaRotation;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else {
-      return false;
-    }
-  };
+  return (
+      /**
+       * @param {ol.Map} map Map.
+       * @param {?ol.FrameState} frameState Frame state.
+       */
+      function(map, frameState) {
+        if (frameState.time < start) {
+          frameState.animate = true;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else if (frameState.time < start + duration) {
+          var delta = 1 - easing((frameState.time - start) / duration);
+          var deltaRotation =
+              sourceRotation - frameState.view2DState.rotation;
+          frameState.animate = true;
+          frameState.view2DState.rotation += delta * deltaRotation;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else {
+          return false;
+        }
+      });
 };
 
 
@@ -110,21 +125,26 @@ ol.animation.zoom = function(options) {
   var duration = goog.isDef(options.duration) ? options.duration : 1000;
   var easing = goog.isDef(options.easing) ?
       options.easing : ol.easing.inAndOut;
-  return function(map, frameState) {
-    if (frameState.time < start) {
-      frameState.animate = true;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else if (frameState.time < start + duration) {
-      var delta = 1 - easing((frameState.time - start) / duration);
-      var deltaResolution =
-          sourceResolution - frameState.view2DState.resolution;
-      frameState.animate = true;
-      frameState.view2DState.resolution += delta * deltaResolution;
-      frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
-      return true;
-    } else {
-      return false;
-    }
-  };
+  return (
+      /**
+       * @param {ol.Map} map Map.
+       * @param {?ol.FrameState} frameState Frame state.
+       */
+      function(map, frameState) {
+        if (frameState.time < start) {
+          frameState.animate = true;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else if (frameState.time < start + duration) {
+          var delta = 1 - easing((frameState.time - start) / duration);
+          var deltaResolution =
+              sourceResolution - frameState.view2DState.resolution;
+          frameState.animate = true;
+          frameState.view2DState.resolution += delta * deltaResolution;
+          frameState.viewHints[ol.ViewHint.ANIMATING] += 1;
+          return true;
+        } else {
+          return false;
+        }
+      });
 };
diff --git a/src/ol/coordinate.js b/src/ol/coordinate.js
index ad60916902..60f339e00e 100644
--- a/src/ol/coordinate.js
+++ b/src/ol/coordinate.js
@@ -35,9 +35,14 @@ ol.coordinate.add = function(coordinate, delta) {
  * @return {ol.CoordinateFormatType} Coordinate format.
  */
 ol.coordinate.createStringXY = function(opt_precision) {
-  return function(coordinate) {
-    return ol.coordinate.toStringXY(coordinate, opt_precision);
-  };
+  return (
+      /**
+       * @param {ol.Coordinate|undefined} coordinate Coordinate.
+       * @return {string} String XY.
+       */
+      function(coordinate) {
+        return ol.coordinate.toStringXY(coordinate, opt_precision);
+      });
 };
 
 
diff --git a/src/ol/imageurlfunction.js b/src/ol/imageurlfunction.js
index 6ec18fbc37..ebddedebdb 100644
--- a/src/ol/imageurlfunction.js
+++ b/src/ol/imageurlfunction.js
@@ -15,15 +15,21 @@ ol.ImageUrlFunctionType;
  * @param {string} baseUrl Base URL (may have query data).
  * @param {Object.<string,*>} params to encode in the url.
  * @param {function(string, Object.<string,*>, ol.Extent, ol.Size,
- *     ol.Projection)} paramsFunction params function.
+ *     ol.Projection): (string|undefined)} paramsFunction params function.
  * @return {ol.ImageUrlFunctionType} Image URL function.
  */
 ol.ImageUrlFunction.createFromParamsFunction =
     function(baseUrl, params, paramsFunction) {
-  return function(extent, size, projection) {
-    return paramsFunction(
-        baseUrl, params, extent, size, projection);
-  };
+  return (
+      /**
+       * @param {ol.Extent} extent Extent.
+       * @param {ol.Size} size Size.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} URL.
+       */
+      function(extent, size, projection) {
+        return paramsFunction(baseUrl, params, extent, size, projection);
+      });
 };
 
 
diff --git a/src/ol/renderer/layerrenderer.js b/src/ol/renderer/layerrenderer.js
index 6f523a59f6..6d509971dc 100644
--- a/src/ol/renderer/layerrenderer.js
+++ b/src/ol/renderer/layerrenderer.js
@@ -266,10 +266,17 @@ ol.renderer.Layer.prototype.updateUsedTiles =
  */
 ol.renderer.Layer.prototype.createGetTileIfLoadedFunction =
     function(isLoadedFunction, tileSource, projection) {
-  return function(z, x, y) {
-    var tile = tileSource.getTile(z, x, y, projection);
-    return isLoadedFunction(tile) ? tile : null;
-  };
+  return (
+      /**
+       * @param {number} z Z.
+       * @param {number} x X.
+       * @param {number} y Y.
+       * @return {ol.Tile} Tile.
+       */
+      function(z, x, y) {
+        var tile = tileSource.getTile(z, x, y, projection);
+        return isLoadedFunction(tile) ? tile : null;
+      });
 };
 
 
diff --git a/src/ol/resolutionconstraint.js b/src/ol/resolutionconstraint.js
index 89a237e748..051da23ee3 100644
--- a/src/ol/resolutionconstraint.js
+++ b/src/ol/resolutionconstraint.js
@@ -20,14 +20,21 @@ ol.ResolutionConstraintType;
 ol.ResolutionConstraint.createContinuous =
     function(power, maxResolution, opt_minResolution) {
   var minResolution = opt_minResolution || 0;
-  return function(resolution, delta, direction) {
-    if (goog.isDef(resolution)) {
-      resolution /= Math.pow(power, delta);
-      return goog.math.clamp(resolution, minResolution, maxResolution);
-    } else {
-      return undefined;
-    }
-  };
+  return (
+      /**
+       * @param {number|undefined} resolution Resolution.
+       * @param {number} delta Delta.
+       * @param {number} direction Direction.
+       * @return {number|undefined} Resolution.
+       */
+      function(resolution, delta, direction) {
+        if (goog.isDef(resolution)) {
+          resolution /= Math.pow(power, delta);
+          return goog.math.clamp(resolution, minResolution, maxResolution);
+        } else {
+          return undefined;
+        }
+      });
 };
 
 
@@ -37,15 +44,23 @@ ol.ResolutionConstraint.createContinuous =
  */
 ol.ResolutionConstraint.createSnapToResolutions =
     function(resolutions) {
-  return function(resolution, delta, direction) {
-    if (goog.isDef(resolution)) {
-      var z = ol.array.linearFindNearest(resolutions, resolution, direction);
-      z = goog.math.clamp(z + delta, 0, resolutions.length - 1);
-      return resolutions[z];
-    } else {
-      return undefined;
-    }
-  };
+  return (
+      /**
+       * @param {number|undefined} resolution Resolution.
+       * @param {number} delta Delta.
+       * @param {number} direction Direction.
+       * @return {number|undefined} Resolution.
+       */
+      function(resolution, delta, direction) {
+        if (goog.isDef(resolution)) {
+          var z =
+              ol.array.linearFindNearest(resolutions, resolution, direction);
+          z = goog.math.clamp(z + delta, 0, resolutions.length - 1);
+          return resolutions[z];
+        } else {
+          return undefined;
+        }
+      });
 };
 
 
@@ -57,25 +72,32 @@ ol.ResolutionConstraint.createSnapToResolutions =
  */
 ol.ResolutionConstraint.createSnapToPower =
     function(power, maxResolution, opt_maxLevel) {
-  return function(resolution, delta, direction) {
-    if (goog.isDef(resolution)) {
-      var offset;
-      if (direction > 0) {
-        offset = 0;
-      } else if (direction < 0) {
-        offset = 1;
-      } else {
-        offset = 0.5;
-      }
-      var oldLevel = Math.floor(
-          Math.log(maxResolution / resolution) / Math.log(power) + offset);
-      var newLevel = Math.max(oldLevel + delta, 0);
-      if (goog.isDef(opt_maxLevel)) {
-        newLevel = Math.min(newLevel, opt_maxLevel);
-      }
-      return maxResolution / Math.pow(power, newLevel);
-    } else {
-      return undefined;
-    }
-  };
+  return (
+      /**
+       * @param {number|undefined} resolution Resolution.
+       * @param {number} delta Delta.
+       * @param {number} direction Direction.
+       * @return {number|undefined} Resolution.
+       */
+      function(resolution, delta, direction) {
+        if (goog.isDef(resolution)) {
+          var offset;
+          if (direction > 0) {
+            offset = 0;
+          } else if (direction < 0) {
+            offset = 1;
+          } else {
+            offset = 0.5;
+          }
+          var oldLevel = Math.floor(
+              Math.log(maxResolution / resolution) / Math.log(power) + offset);
+          var newLevel = Math.max(oldLevel + delta, 0);
+          if (goog.isDef(opt_maxLevel)) {
+            newLevel = Math.min(newLevel, opt_maxLevel);
+          }
+          return maxResolution / Math.pow(power, newLevel);
+        } else {
+          return undefined;
+        }
+      });
 };
diff --git a/src/ol/rotationconstraint.js b/src/ol/rotationconstraint.js
index c297e13608..820f6cf3c8 100644
--- a/src/ol/rotationconstraint.js
+++ b/src/ol/rotationconstraint.js
@@ -28,14 +28,20 @@ ol.RotationConstraint.none = function(rotation, delta) {
  */
 ol.RotationConstraint.createSnapToN = function(n) {
   var theta = 2 * Math.PI / n;
-  return function(rotation, delta) {
-    if (goog.isDef(rotation)) {
-      rotation = Math.floor((rotation + delta) / theta + 0.5) * theta;
-      return rotation;
-    } else {
-      return undefined;
-    }
-  };
+  return (
+      /**
+       * @param {number|undefined} rotation Rotation.
+       * @param {number} delta Delta.
+       * @return {number|undefined} Rotation.
+       */
+      function(rotation, delta) {
+        if (goog.isDef(rotation)) {
+          rotation = Math.floor((rotation + delta) / theta + 0.5) * theta;
+          return rotation;
+        } else {
+          return undefined;
+        }
+      });
 };
 
 
@@ -45,15 +51,21 @@ ol.RotationConstraint.createSnapToN = function(n) {
  */
 ol.RotationConstraint.createSnapToZero = function(opt_tolerance) {
   var tolerance = opt_tolerance || 0.1;
-  return function(rotation, delta) {
-    if (goog.isDef(rotation)) {
-      if (Math.abs(rotation + delta) <= tolerance) {
-        return 0;
-      } else {
-        return rotation + delta;
-      }
-    } else {
-      return undefined;
-    }
-  };
+  return (
+      /**
+       * @param {number|undefined} rotation Rotation.
+       * @param {number} delta Delta.
+       * @return {number|undefined} Rotation.
+       */
+      function(rotation, delta) {
+        if (goog.isDef(rotation)) {
+          if (Math.abs(rotation + delta) <= tolerance) {
+            return 0;
+          } else {
+            return rotation + delta;
+          }
+        } else {
+          return undefined;
+        }
+      });
 };
diff --git a/src/ol/source/bingmapssource.js b/src/ol/source/bingmapssource.js
index c190397441..1684940a15 100644
--- a/src/ol/source/bingmapssource.js
+++ b/src/ol/source/bingmapssource.js
@@ -88,16 +88,22 @@ ol.source.BingMaps.prototype.handleImageryMetadataResponse =
                 var imageUrl = resource.imageUrl
                     .replace('{subdomain}', subdomain)
                     .replace('{culture}', culture);
-                return function(tileCoord, projection) {
-                  goog.asserts.assert(ol.projection.equivalent(
-                      projection, this.getProjection()));
-                  if (goog.isNull(tileCoord)) {
-                    return undefined;
-                  } else {
-                    return imageUrl.replace(
-                        '{quadkey}', tileCoord.quadKey());
-                  }
-                };
+                return (
+                    /**
+                     * @param {ol.TileCoord} tileCoord Tile coordinate.
+                     * @param {ol.Projection} projection Projection.
+                     * @return {string|undefined} Tile URL.
+                     */
+                    function(tileCoord, projection) {
+                      goog.asserts.assert(ol.projection.equivalent(
+                          projection, this.getProjection()));
+                      if (goog.isNull(tileCoord)) {
+                        return undefined;
+                      } else {
+                        return imageUrl.replace(
+                            '{quadkey}', tileCoord.quadKey());
+                      }
+                    });
               })));
 
   var transform = ol.projection.getTransformFromProjections(
diff --git a/src/ol/source/staticimagesource.js b/src/ol/source/staticimagesource.js
index 74dd079a63..17791719fd 100644
--- a/src/ol/source/staticimagesource.js
+++ b/src/ol/source/staticimagesource.js
@@ -60,7 +60,14 @@ ol.source.StaticImage.prototype.getImage =
  * @return {ol.ImageUrlFunctionType} Function.
  */
 ol.source.StaticImage.createImageFunction = function(url) {
-  return function(extent, size, projection) {
-    return url;
-  };
+  return (
+      /**
+       * @param {ol.Extent} extent Extent.
+       * @param {ol.Size} size Size.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} URL.
+       */
+      function(extent, size, projection) {
+        return url;
+      });
 };
diff --git a/src/ol/source/wmtssource.js b/src/ol/source/wmtssource.js
index 91fed7ba60..9fdc72427d 100644
--- a/src/ol/source/wmtssource.js
+++ b/src/ol/source/wmtssource.js
@@ -73,27 +73,32 @@ ol.source.WMTS = function(options) {
    * @return {ol.TileUrlFunctionType} Tile URL function.
    */
   function createFromWMTSTemplate(template) {
-    return function(tileCoord) {
-      if (goog.isNull(tileCoord)) {
-        return undefined;
-      } else {
-        var localContext = {
-          'TileMatrix': tileGrid.getMatrixId(tileCoord.z),
-          'TileCol': tileCoord.x,
-          'TileRow': tileCoord.y
-        };
-        if (requestEncoding != ol.source.WMTSRequestEncoding.KVP) {
-          goog.object.extend(localContext, context);
-        }
-        var url = template;
-        for (var key in localContext) {
-          // FIXME: should we filter properties with hasOwnProperty?
-          url = url.replace('{' + key + '}', localContext[key])
-              .replace('%7B' + key + '%7D', localContext[key]);
-        }
-        return url;
-      }
-    };
+    return (
+        /**
+         * @param {ol.TileCoord} tileCoord Tile coordinate.
+         * @return {string|undefined} Tile URL.
+         */
+        function(tileCoord) {
+          if (goog.isNull(tileCoord)) {
+            return undefined;
+          } else {
+            var localContext = {
+              'TileMatrix': tileGrid.getMatrixId(tileCoord.z),
+              'TileCol': tileCoord.x,
+              'TileRow': tileCoord.y
+            };
+            if (requestEncoding != ol.source.WMTSRequestEncoding.KVP) {
+              goog.object.extend(localContext, context);
+            }
+            var url = template;
+            for (var key in localContext) {
+              // FIXME: should we filter properties with hasOwnProperty?
+              url = url.replace('{' + key + '}', localContext[key])
+                  .replace('%7B' + key + '%7D', localContext[key]);
+            }
+            return url;
+          }
+        });
   }
 
   var tileUrlFunction = ol.TileUrlFunction.nullTileUrlFunction;
diff --git a/src/ol/tileurlfunction.js b/src/ol/tileurlfunction.js
index 47db38f273..5404e3a80b 100644
--- a/src/ol/tileurlfunction.js
+++ b/src/ol/tileurlfunction.js
@@ -18,15 +18,21 @@ ol.TileUrlFunctionType;
  * @return {ol.TileUrlFunctionType} Tile URL function.
  */
 ol.TileUrlFunction.createFromTemplate = function(template) {
-  return function(tileCoord) {
-    if (goog.isNull(tileCoord)) {
-      return undefined;
-    } else {
-      return template.replace('{z}', tileCoord.z)
-                      .replace('{x}', tileCoord.x)
-                      .replace('{y}', tileCoord.y);
-    }
-  };
+  return (
+      /**
+       * @param {ol.TileCoord} tileCoord Tile Coordinate.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} Tile URL.
+       */
+      function(tileCoord, projection) {
+        if (goog.isNull(tileCoord)) {
+          return undefined;
+        } else {
+          return template.replace('{z}', '' + tileCoord.z)
+                         .replace('{x}', '' + tileCoord.x)
+                         .replace('{y}', '' + tileCoord.y);
+        }
+      });
 };
 
 
@@ -48,14 +54,21 @@ ol.TileUrlFunction.createFromTileUrlFunctions = function(tileUrlFunctions) {
   if (tileUrlFunctions.length === 1) {
     return tileUrlFunctions[0];
   }
-  return function(tileCoord, projection) {
-    if (goog.isNull(tileCoord)) {
-      return undefined;
-    } else {
-      var index = goog.math.modulo(tileCoord.hash(), tileUrlFunctions.length);
-      return tileUrlFunctions[index].call(this, tileCoord, projection);
-    }
-  };
+  return (
+      /**
+       * @param {ol.TileCoord} tileCoord Tile Coordinate.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} Tile URL.
+       */
+      function(tileCoord, projection) {
+        if (goog.isNull(tileCoord)) {
+          return undefined;
+        } else {
+          var index =
+              goog.math.modulo(tileCoord.hash(), tileUrlFunctions.length);
+          return tileUrlFunctions[index].call(this, tileCoord, projection);
+        }
+      });
 };
 
 
@@ -69,20 +82,26 @@ ol.TileUrlFunction.createFromTileUrlFunctions = function(tileUrlFunctions) {
 ol.TileUrlFunction.createFromParamsFunction =
     function(baseUrl, params, paramsFunction) {
   var tmpExtent = ol.extent.createEmptyExtent();
-  return function(tileCoord, projection) {
-    if (goog.isNull(tileCoord)) {
-      return undefined;
-    } else {
-      var tileGrid = this.getTileGrid();
-      if (goog.isNull(tileGrid)) {
-        tileGrid = ol.tilegrid.getForProjection(projection);
-      }
-      var size = tileGrid.getTileSize(tileCoord.z);
-      var extent = tileGrid.getTileCoordExtent(tileCoord, tmpExtent);
-      return paramsFunction.call(this, baseUrl, params,
-          extent, size, projection);
-    }
-  };
+  return (
+      /**
+       * @param {ol.TileCoord} tileCoord Tile Coordinate.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} Tile URL.
+       */
+      function(tileCoord, projection) {
+        if (goog.isNull(tileCoord)) {
+          return undefined;
+        } else {
+          var tileGrid = this.getTileGrid();
+          if (goog.isNull(tileGrid)) {
+            tileGrid = ol.tilegrid.getForProjection(projection);
+          }
+          var size = tileGrid.getTileSize(tileCoord.z);
+          var extent = tileGrid.getTileCoordExtent(tileCoord, tmpExtent);
+          return paramsFunction.call(this, baseUrl, params,
+              extent, size, projection);
+        }
+      });
 };
 
 
@@ -105,16 +124,22 @@ ol.TileUrlFunction.nullTileUrlFunction = function(tileCoord, projection) {
 ol.TileUrlFunction.withTileCoordTransform =
     function(transformFn, tileUrlFunction) {
   var tmpTileCoord = new ol.TileCoord(0, 0, 0);
-  return function(tileCoord, projection) {
-    if (goog.isNull(tileCoord)) {
-      return undefined;
-    } else {
-      return tileUrlFunction.call(
-          this,
-          transformFn.call(this, tileCoord, projection, tmpTileCoord),
-          projection);
-    }
-  };
+  return (
+      /**
+       * @param {ol.TileCoord} tileCoord Tile Coordinate.
+       * @param {ol.Projection} projection Projection.
+       * @return {string|undefined} Tile URL.
+       */
+      function(tileCoord, projection) {
+        if (goog.isNull(tileCoord)) {
+          return undefined;
+        } else {
+          return tileUrlFunction.call(
+              this,
+              transformFn.call(this, tileCoord, projection, tmpTileCoord),
+              projection);
+        }
+      });
 };
 
 
diff --git a/src/ol/view2d.js b/src/ol/view2d.js
index e377b0a223..a75107635d 100644
--- a/src/ol/view2d.js
+++ b/src/ol/view2d.js
@@ -231,12 +231,17 @@ ol.View2D.prototype.getResolutionForValueFunction = function(opt_power) {
   var maxResolution = this.maxResolution_;
   var minResolution = this.minResolution_;
   var max = Math.log(maxResolution / minResolution) / Math.log(power);
-  return function(value) {
-    var resolution = maxResolution / Math.pow(power, value * max);
-    goog.asserts.assert(resolution >= minResolution &&
-        resolution <= maxResolution);
-    return resolution;
-  };
+  return (
+      /**
+       * @param {number} value Value.
+       * @return {number} Resolution.
+       */
+      function(value) {
+        var resolution = maxResolution / Math.pow(power, value * max);
+        goog.asserts.assert(resolution >= minResolution &&
+            resolution <= maxResolution);
+        return resolution;
+      });
 };
 
 
@@ -264,11 +269,17 @@ ol.View2D.prototype.getValueForResolutionFunction = function(opt_power) {
   var maxResolution = this.maxResolution_;
   var minResolution = this.minResolution_;
   var max = Math.log(maxResolution / minResolution) / Math.log(power);
-  return function(resolution) {
-    var value = (Math.log(maxResolution / resolution) / Math.log(power)) / max;
-    goog.asserts.assert(value >= 0 && value <= 1);
-    return value;
-  };
+  return (
+      /**
+       * @param {number} resolution Resolution.
+       * @return {number} Value.
+       */
+      function(resolution) {
+        var value =
+            (Math.log(maxResolution / resolution) / Math.log(power)) / max;
+        goog.asserts.assert(value >= 0 && value <= 1);
+        return value;
+      });
 };