blob: 7228282e4e4b57bc739fb7a942290f01b735dce8 [file] [log] [blame]
/**
* @license
* Copyright 2019 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import {Finalizable} from '../registry';
import {
EventCallback,
EventEmitterService,
UnsubscribeMethod,
} from './gr-event-interface';
/**
* An lite implementation of
* https://nodejs.org/api/events.html#events_class_eventemitter.
*
* This is unrelated to the native DOM events, you should use it when you want
* to enable EventEmitter interface on any class.
*
* @example
*
* class YourClass extends EventEmitter {
* // now all instance of YourClass will have this EventEmitter interface
* }
*
*/
export class EventEmitter implements EventEmitterService, Finalizable {
private _listenersMap = new Map<string, EventCallback[]>();
finalize() {
this.removeAllListeners();
}
/**
* Register an event listener to an event.
*/
addListener(eventName: string, cb: EventCallback): UnsubscribeMethod {
if (!eventName || !cb) {
console.warn('A valid eventname and callback is required!');
return () => {};
}
const listeners = this._listenersMap.get(eventName) || [];
listeners.push(cb);
this._listenersMap.set(eventName, listeners);
return () => {
this.off(eventName, cb);
};
}
/**
* Alias for addListener.
*/
on(eventName: string, cb: EventCallback): UnsubscribeMethod {
return this.addListener(eventName, cb);
}
/**
* Attach event handler only once. Automatically removed.
*/
once(eventName: string, cb: EventCallback): UnsubscribeMethod {
// eslint-disable-next-line @typescript-eslint/no-explicit-any
const onceWrapper = (...args: any[]) => {
cb(...args);
this.off(eventName, onceWrapper);
};
return this.on(eventName, onceWrapper);
}
/**
* De-register an event listener to an event.
*/
removeListener(eventName: string, cb: EventCallback): void {
let listeners = this._listenersMap.get(eventName) || [];
listeners = listeners.filter(listener => listener !== cb);
this._listenersMap.set(eventName, listeners);
}
/**
* Alias to removeListener
*/
off(eventName: string, cb: EventCallback): void {
this.removeListener(eventName, cb);
}
/**
* Synchronously calls each of the listeners registered for
* the event named eventName, in the order they were registered,
* passing the supplied detail to each.
*
* @return true if the event had listeners, false otherwise.
*/
// eslint-disable-next-line @typescript-eslint/no-explicit-any
emit(eventName: string, detail: any): boolean {
const listeners = this._listenersMap.get(eventName) || [];
for (const listener of listeners) {
try {
listener(detail);
} catch (e) {
console.error(e);
}
}
return listeners.length !== 0;
}
/**
* Alias to emit.
*/
// eslint-disable-next-line @typescript-eslint/no-explicit-any
dispatch(eventName: string, detail: any): boolean {
return this.emit(eventName, detail);
}
/**
* Remove listeners for a specific event or all.
*
* @param eventName if not provided, will remove all
*/
removeAllListeners(eventName?: string): void {
if (eventName) {
this._listenersMap.set(eventName, []);
} else {
this._listenersMap = new Map<string, EventCallback[]>();
}
}
}