Use Infinity rather than undefined to drop tiles

src/ol/map.js

@@ -455,17 +455,17 @@ ol.Map.prototype.getOverlayContainer = function() {
  * @param {ol.Tile} tile Tile.
  * @param {string} tileSourceKey Tile source key.
  * @param {ol.Coordinate} tileCenter Tile center.
- * @return {number|undefined} Tile priority.
+ * @return {number} Tile priority.
  */
 ol.Map.prototype.getTilePriority = function(tile, tileSourceKey, tileCenter) {
   var frameState = this.frameState_;
   if (goog.isNull(frameState) || !(tileSourceKey in frameState.wantedTiles)) {
-    return undefined;
+    return ol.TileQueue.DROP;
   }
   var zKey = tile.tileCoord.z.toString();
   if (!(zKey in frameState.wantedTiles[tileSourceKey]) ||
       !frameState.wantedTiles[tileSourceKey][zKey].contains(tile.tileCoord)) {
-    return undefined;
+    return ol.TileQueue.DROP;
   }
   var center = frameState.view2DState.center;
   var deltaX = tileCenter.x - center.x;

src/ol/tilequeue.js

@@ -21,7 +21,7 @@ goog.require('ol.TileState');
 
 
 /**
- * @typedef {function(ol.Tile, string, ol.Coordinate): (number|undefined)}
+ * @typedef {function(ol.Tile, string, ol.Coordinate): number}
  */
 ol.TilePriorityFunction;
 
@@ -67,6 +67,12 @@ ol.TileQueue = function(tilePriorityFunction) {
 };
 
 
+/**
+ * @const {number}
+ */
+ol.TileQueue.DROP = Infinity;
+
+
 /**
  * FIXME empty description for jsdoc
  */
@@ -112,7 +118,7 @@ ol.TileQueue.prototype.enqueue = function(tile, tileSourceKey, tileCenter) {
   var tileKey = tile.getKey();
   if (!(tileKey in this.queuedTileKeys_)) {
     var priority = this.tilePriorityFunction_(tile, tileSourceKey, tileCenter);
-    if (goog.isDef(priority)) {
+    if (priority != ol.TileQueue.DROP) {
       this.heap_.push([priority, tile, tileSourceKey, tileCenter]);
       this.queuedTileKeys_[tileKey] = true;
       this.siftDown_(0, this.heap_.length - 1);
@@ -252,7 +258,7 @@ ol.TileQueue.prototype.reprioritize = function() {
     tileSourceKey = /** @type {string} */ (node[2]);
     tileCenter = /** @type {ol.Coordinate} */ (node[3]);
     priority = this.tilePriorityFunction_(tile, tileSourceKey, tileCenter);
-    if (goog.isDef(priority)) {
+    if (priority != ol.TileQueue.DROP) {
       node[0] = priority;
     } else {
       goog.array.removeAt(heap, i);

test/spec/ol/tilequeue.test.js

@@ -53,7 +53,7 @@ describe('ol.TileQueue', function() {
       var i = 0;
       tq.tilePriorityFunction_ = function() {
         if ((i++) % 2 === 0) {
-          return undefined;
+          return ol.TileQueue.DROP;
         }
         return Math.floor(Math.random() * 100);
       };