Clarification and use callbacks in examples

examples/vector-esri.js

@@ -56,7 +56,7 @@ const styleCache = {
 };
 
 const vectorSource = new VectorSource({
-  loader: function (extent, resolution, projection) {
+  loader: function (extent, resolution, projection, success, failure) {
     const url =
       serviceUrl +
       layer +
@@ -83,6 +83,7 @@ const vectorSource = new VectorSource({
           alert(
             response.error.message + '\n' + response.error.details.join('\n')
           );
+          failure();
         } else {
           // dataProjection will be read from document
           const features = esrijsonFormat.readFeatures(response, {
@@ -91,8 +92,10 @@ const vectorSource = new VectorSource({
           if (features.length > 0) {
             vectorSource.addFeatures(features);
           }
+          success(features);
         }
       },
+      error: failure,
     });
   },
   strategy: tileStrategy(

examples/vector-osm.js

@@ -74,7 +74,7 @@ const styles = {
 
 const vectorSource = new VectorSource({
   format: new OSMXML(),
-  loader: function (extent, resolution, projection) {
+  loader: function (extent, resolution, projection, success, failure) {
     const epsg4326Extent = transformExtent(extent, projection, 'EPSG:4326');
     const client = new XMLHttpRequest();
     client.open('POST', 'https://overpass-api.de/api/interpreter');
@@ -83,7 +83,9 @@ const vectorSource = new VectorSource({
         featureProjection: map.getView().getProjection(),
       });
       vectorSource.addFeatures(features);
+      success(features);
     });
+    client.addEventListener('error', failure);
     const query =
       '(node(' +
       epsg4326Extent[1] +

src/ol/featureloader.js

@@ -19,8 +19,8 @@ let withCredentials = false;
  * the area to be loaded, a `{number}` representing the resolution (map units per pixel), an
  * {@link module:ol/proj/Projection} for the projection, an optional success callback that should get
  * the loaded features passed as an argument and an optional failure callback with no arguments. If
- * the callbacks are not used, the corresponding vector source will not fire `'featuresloadstart'`,
- * `'featuresloadend'` and `'featuresloaderror'` events. `this` within the function is bound to the
+ * the callbacks are not used, the corresponding vector source will not fire `'featuresloadend'` and
+ * `'featuresloaderror'` events. `this` within the function is bound to the
  * {@link module:ol/source/Vector} it's called from.
  *
  * The function is responsible for loading the features and adding them to the

src/ol/source/Vector.js

@@ -72,7 +72,7 @@ export class VectorSourceEvent extends Event {
  * @property {import("../featureloader.js").FeatureLoader} [loader]
  * The loader function used to load features, from a remote source for example.
  * If this is not set and `url` is set, the source will create and use an XHR
- * feature loader. The `'featuresloadstart'`, `'featuresloadend'` and `'featuresloaderror'` events
+ * feature loader. The `'featuresloadend'` and `'featuresloaderror'` events
  * will only fire if the `success` and `failure` callbacks are used.
  *
  * Example: