Merge pull request #558 from Harbour-Enterprises/nick/har-9817-add-once-to-emitter

HAR-9817 - Add .once to custom event emitter in editor.js

Author: edoversb

packages/super-editor/src/core/EventEmitter.js

@@ -6,8 +6,9 @@ export class EventEmitter {
 
   /**
    * Subscribe to the event.
-   * @param name Event name.
-   * @param fn Callback.
+   * @param {string} name Event name.
+   * @param {(...args: any[]) => void} fn Callback.
+   * @returns {void}
    */
   on(name, fn) {
     const callbacks = this.#events.get(name);
@@ -17,8 +18,9 @@ export class EventEmitter {
 
   /**
    * Emit event.
-   * @param name Event name.
-   * @param args Arguments.
+   * @param {string} name Event name.
+   * @param {...any} args – Arguments to pass to each listener.
+   * @returns {void}
    */
   emit(name, ...args) {
     const callbacks = this.#events.get(name);
@@ -31,8 +33,9 @@ export class EventEmitter {
   /**
    * Remove a specific callback from event
    * or all event subscriptions.
-   * @param name Event name.
-   * @param fn Callback.
+   * @param {string} name Event name.
+   * @param {(...args: any[]) => void} fn Callback.
+   * @returns {void}
    */
   off(name, fn) {
     const callbacks = this.#events.get(name);
@@ -47,6 +50,20 @@ export class EventEmitter {
     }
   }
 
+  /**
+   * Subscribe to an event that will be called only once.
+   * @param {string} name Event name.
+   * @param {(...args: any[]) => void} fn Callback.
+   * @returns {void}
+   */
+  once(name, fn) {
+    const wrapper = (...args) => {
+      this.off(name, wrapper);
+      fn.apply(this, args);
+    };
+    this.on(name, wrapper)
+  }
+
   /**
    * Remove all registered events and subscriptions.
    */