sources and layers.

src/ol/source/Image.js

@@ -38,6 +38,10 @@ export const ImageSourceEventType = {
   IMAGELOADERROR: 'imageloaderror',
 };
 
+/**
+ * @typedef {'imageloadend'|'imageloaderror'|'imageloadstart'} ImageSourceEventTypes
+ */
+
 /**
  * @classdesc
  * Events emitted by {@link module:ol/source/Image~ImageSource} instances are instances of this
@@ -89,6 +93,13 @@ class ImageSource extends Source {
       state: options.state,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<ImageSourceEventTypes, ImageSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {Array<number>}

src/ol/source/Tile.js

@@ -52,6 +52,13 @@ class TileSource extends Source {
       wrapX: options.wrapX,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("./TileEventType").TileSourceEventTypes, TileSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {boolean}

src/ol/source/TileEventType.js

@@ -28,3 +28,7 @@ export default {
    */
   TILELOADERROR: 'tileloaderror',
 };
+
+/**
+ * @typedef {'tileloadstart'|'tileloadend'|'tileloaderror'} TileSourceEventTypes
+ */

src/ol/source/Vector.js

@@ -177,6 +177,13 @@ class VectorSource extends Source {
       wrapX: options.wrapX !== undefined ? options.wrapX : true,
     });
 
+    /***
+     * @type {import("../Observable").OnSignature<import("../Observable").EventTypes, import("../events/Event.js").default> &
+     *   import("../Observable").OnSignature<import("../ObjectEventType").Types, import("../Object").ObjectEvent> &
+     *   import("../Observable").OnSignature<import("./VectorEventType").VectorSourceEventTypes, VectorSourceEvent>}
+     */
+    this.on;
+
     /**
      * @private
      * @type {import("../featureloader.js").FeatureLoader}

src/ol/source/VectorEventType.js

@@ -56,3 +56,7 @@ export default {
    */
   FEATURESLOADERROR: 'featuresloaderror',
 };
+
+/**
+ * @typedef {'addfeature'|'clear'|'removefeature'|'featuresloadstart'|'featuresloadend'|'featuresloaderror'} VectorSourceEventTypes
+ */