/* Copyright 2019 Google LLC Use of this source code is governed by an MIT-style license that can be found in the LICENSE file or at https://opensource.org/licenses/MIT. */ import {WorkboxEvent, WorkboxEventMap} from './WorkboxEvent.js'; export type ListenerCallback = (event: WorkboxEvent) => any; /** * A minimal `EventTarget` shim. * This is necessary because not all browsers support constructable * `EventTarget`, so using a real `EventTarget` will error. * @private */ export class WorkboxEventTarget { private readonly _eventListenerRegistry: Map< keyof WorkboxEventMap, Set > = new Map(); /** * @param {string} type * @param {Function} listener * @private */ addEventListener( type: K, listener: (event: WorkboxEventMap[K]) => any, ): void { const foo = this._getEventListenersByType(type); foo.add(listener as ListenerCallback); } /** * @param {string} type * @param {Function} listener * @private */ removeEventListener( type: K, listener: (event: WorkboxEventMap[K]) => any, ): void { this._getEventListenersByType(type).delete(listener as ListenerCallback); } /** * @param {Object} event * @private */ dispatchEvent(event: WorkboxEvent): void { event.target = this; const listeners = this._getEventListenersByType(event.type); for (const listener of listeners) { listener(event); } } /** * Returns a Set of listeners associated with the passed event type. * If no handlers have been registered, an empty Set is returned. * * @param {string} type The event type. * @return {Set} An array of handler functions. * @private */ private _getEventListenersByType(type: keyof WorkboxEventMap) { if (!this._eventListenerRegistry.has(type)) { this._eventListenerRegistry.set(type, new Set()); } return this._eventListenerRegistry.get(type)!; } }