Add hasListener check around dispatchEvent calls

src/ol/Object.js

@@ -172,9 +172,13 @@ class BaseObject extends Observable {
   notify(key, oldValue) {
     let eventType;
     eventType = `change:${key}`;
-    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    if (this.hasListener(eventType)) {
+      this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    }
     eventType = ObjectEventType.PROPERTYCHANGE;
-    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    if (this.hasListener(eventType)) {
+      this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    }
   }
 
   /**

src/ol/source/Image.js

@@ -240,27 +240,25 @@ class ImageSource extends Source {
    */
   handleImageChange(event) {
     const image = /** @type {import("../Image.js").default} */ (event.target);
+    let type;
     switch (image.getState()) {
       case ImageState.LOADING:
         this.loading = true;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADSTART, image)
-        );
+        type = ImageSourceEventType.IMAGELOADSTART;
         break;
       case ImageState.LOADED:
         this.loading = false;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADEND, image)
-        );
+        type = ImageSourceEventType.IMAGELOADEND;
         break;
       case ImageState.ERROR:
         this.loading = false;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADERROR, image)
-        );
+        type = ImageSourceEventType.IMAGELOADERROR;
         break;
       default:
-      // pass
+        return;
+    }
+    if (this.hasListener(type)) {
+      this.dispatchEvent(new ImageSourceEvent(type, image));
     }
   }
 }

src/ol/source/Vector.js

@@ -457,10 +457,12 @@ class VectorSource extends Source {
       this.featuresRtree_.load(extents, geometryFeatures);
     }
 
-    for (let i = 0, length = newFeatures.length; i < length; i++) {
-      this.dispatchEvent(
-        new VectorSourceEvent(VectorEventType.ADDFEATURE, newFeatures[i])
-      );
+    if (this.hasListener(VectorEventType.ADDFEATURE)) {
+      for (let i = 0, length = newFeatures.length; i < length; i++) {
+        this.dispatchEvent(
+          new VectorSourceEvent(VectorEventType.ADDFEATURE, newFeatures[i])
+        );
+      }
     }
   }