Avoid creating event object when nobody is listening

src/ol/events/Target.js

@@ -83,15 +83,17 @@ class Target extends Disposable {
    * @api
    */
   dispatchEvent(event) {
-    /** @type {import("./Event.js").default|Event} */
+    const isString = typeof event === 'string';
-    const evt = typeof event === 'string' ? new Event(event) : event;
+    const type = isString ? event : event.type;
-    const type = evt.type;
+    const listeners = this.listeners_ && this.listeners_[type];
+    if (!listeners) {
+      return;
+    }
+
+    const evt = isString ? new Event(event) : /** @type {Event} */ (event);
     if (!evt.target) {
       evt.target = this.eventTarget_ || this;
     }
-    const listeners = this.listeners_ && this.listeners_[type];
-    let propagate;
-    if (listeners) {
     const dispatching = this.dispatching_ || (this.dispatching_ = {});
     const pendingRemovals =
       this.pendingRemovals_ || (this.pendingRemovals_ = {});
@@ -100,6 +102,7 @@ class Target extends Disposable {
       pendingRemovals[type] = 0;
     }
     ++dispatching[type];
+    let propagate;
     for (let i = 0, ii = listeners.length; i < ii; ++i) {
       if ('handleEvent' in listeners[i]) {
         propagate = /** @type {import("../events.js").ListenerObject} */ (
@@ -115,8 +118,7 @@ class Target extends Disposable {
         break;
       }
     }
-      --dispatching[type];
+    if (--dispatching[type] === 0) {
-      if (dispatching[type] === 0) {
       let pr = pendingRemovals[type];
       delete pendingRemovals[type];
       while (pr--) {
@@ -126,7 +128,6 @@ class Target extends Disposable {
     }
     return propagate;
   }
-  }
 
   /**
    * Clean up.