Added once helper to EventEmitter

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Piral Changelog
 
+## 1.3.2 (tbd)
+
+- Added `once` as convenience methods to `EventEmitter`
+
 ## 1.3.1 (October 19, 2023)
 
 - Updated behavior with unresolved inherited dependencies (#633)

src/framework/piral-base/src/api.ts

@@ -4,6 +4,7 @@ import type { PiletMetadata, EventEmitter, PiletApi, PiletApiExtender } from './
 export function initializeApi(target: PiletMetadata, events: EventEmitter): PiletApi {
   return {
     on: events.on,
+    once: events.once,
     off: events.off,
     emit: events.emit,
     meta: __assign({}, target),

src/framework/piral-base/src/events.ts

@@ -22,6 +22,13 @@ export function createListener(state: any = {}): EventEmitter {
       eventListeners.push([callback, listener]);
       return this;
     },
+    once(type, callback) {
+      const cb = (ev: any) => {
+        this.off(type, cb);
+        callback(ev);
+      };
+      return this.on(type, cb);
+    },
     off(type, callback) {
       const [listener] = eventListeners.filter((m) => m[0] === callback);
 
@@ -33,12 +40,16 @@ export function createListener(state: any = {}): EventEmitter {
       return this;
     },
     emit(type, arg) {
-      const ce = document.createEvent('CustomEvent');
-      ce.initCustomEvent(nameOf(type), false, false, {
-        arg,
-        state,
-      });
-      document.body.dispatchEvent(ce);
+      document.body.dispatchEvent(
+        new CustomEvent(nameOf(type), {
+          bubbles: false,
+          cancelable: false,
+          detail: {
+            arg,
+            state,
+          },
+        }),
+      );
       return this;
     },
   };

src/framework/piral-base/src/types/api.ts

@@ -36,6 +36,12 @@ export interface EventEmitter {
    * @param callback The callback to trigger.
    */
   on<K extends keyof PiralEventMap>(type: K, callback: Listener<PiralEventMap[K]>): EventEmitter;
+  /**
+   * Attaches a new event listener that is removed once the event fired.
+   * @param type The type of the event to listen for.
+   * @param callback The callback to trigger.
+   */
+  once<K extends keyof PiralEventMap>(type: K, callback: Listener<PiralEventMap[K]>): EventEmitter;
   /**
    * Detaches an existing event listener.
    * @param type The type of the event to listen for.