Add hasListener check around dispatchEvent calls

src/ol/Object.js

@@ -172,10 +172,14 @@ class BaseObject extends Observable {
   notify(key, oldValue) {
     let eventType;
     eventType = `change:${key}`;
+    if (this.hasListener(eventType)) {
       this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    }
     eventType = ObjectEventType.PROPERTYCHANGE;
+    if (this.hasListener(eventType)) {
       this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
     }
+  }
 
   /**
    * @param {string} key Key name.

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(
+        type = ImageSourceEventType.IMAGELOADSTART;
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADSTART, image)
-        );
         break;
       case ImageState.LOADED:
         this.loading = false;
-        this.dispatchEvent(
+        type = ImageSourceEventType.IMAGELOADEND;
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADEND, image)
-        );
         break;
       case ImageState.ERROR:
         this.loading = false;
-        this.dispatchEvent(
+        type = ImageSourceEventType.IMAGELOADERROR;
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADERROR, image)
-        );
         break;
       default:
-      // pass
+        return;
+    }
+    if (this.hasListener(type)) {
+      this.dispatchEvent(new ImageSourceEvent(type, image));
     }
   }
 }

src/ol/source/Vector.js

@@ -457,12 +457,14 @@ class VectorSource extends Source {
       this.featuresRtree_.load(extents, geometryFeatures);
     }
 
+    if (this.hasListener(VectorEventType.ADDFEATURE)) {
       for (let i = 0, length = newFeatures.length; i < length; i++) {
         this.dispatchEvent(
           new VectorSourceEvent(VectorEventType.ADDFEATURE, newFeatures[i])
         );
       }
     }
+  }
 
   /**
    * @param {!Collection<import("../Feature.js").default<Geometry>>} collection Collection.