notjQuery.js: Return a promise in trigger()

This allows callers to e.g. cleanup after the bubbling phase.
It is now also possible to disallow cancellation and prevent
bubbling. Cancellation makes only sense now to begin with,
as the resolved value will indicate whether a listener called
`preventDefault()` or not.

Author: nilmerg

asset/js/notjQuery.js

@@ -81,19 +81,30 @@ define(function () {
         /**
          * Trigger a custom event on the element, asynchronously
          *
-         * The event will bubble and is not cancelable.
+         * The returned promise will be resolved with `false` only if the event
+         * is cancelable and was canceled by a listener; otherwise `true`.
          *
          * @param {string} type
          * @param {{}} detail
+         * @param {boolean} cancelable
+         * @param {boolean} bubbles
+         * @return {Promise<boolean>}
          */
-        trigger(type, detail = null) {
-            setTimeout(() => {
-                this.element.dispatchEvent(new CustomEvent(type, {
-                    cancelable: true, // TODO: this should depend on whether it's a native or custom event
-                    bubbles: true,
-                    detail: detail
-                }));
-            }, 0);
+        trigger(type, detail = null, cancelable = true, bubbles = true) {
+            return new Promise((resolve, reject) => {
+                setTimeout(() => {
+                    try {
+                        const proceed = this.element.dispatchEvent(new CustomEvent(type, {
+                            cancelable: cancelable,
+                            bubbles: bubbles,
+                            detail: detail
+                        }));
+                        resolve(proceed);
+                    } catch (error) {
+                        reject(error);
+                    }
+                }, 0);
+            });
         }
 
         /**