BetterDiscordApp-v2/common/modules/async-eventemitter.js

69 lines
2.0 KiB
JavaScript

/**
* BetterDiscord Async EventEmitter
* Copyright (c) 2015-present Jiiks/JsSucks - https://github.com/Jiiks / https://github.com/JsSucks
* All rights reserved.
* https://betterdiscord.net
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
import EventEmitter from 'events';
/**
* Extends Node.js' EventEmitter to call event listeners asyncronously.
*/
export default class AsyncEventEmitter extends EventEmitter {
/**
* Emits an event.
* @param {String} event The event to emit
* @param {Any} ...data Data to be passed to event listeners
* @return {Promise}
*/
async emit(event, ...data) {
let listeners = this._events[event] || [];
listeners = Array.isArray(listeners) ? listeners : [listeners];
// Special treatment of internal newListener and removeListener events
if(event === 'newListener' || event === 'removeListener') {
data = [{
event: data,
fn: err => {
if (err) throw err;
}
}];
}
for (let listener of listeners) {
await listener.apply(this, data);
}
}
/**
* Adds an event listener that will be removed when it is called and therefore only be called once.
* If a callback is not specified a promise that is resolved once the event is emitted is returned.
*/
once(event, callback) {
if (callback) {
// If a callback was specified add this event as normal
return EventEmitter.prototype.once.apply(this, arguments);
}
// Otherwise return a promise that is resolved once this event is emitted
return new Promise((resolve, reject) => {
EventEmitter.prototype.once.call(this, event, data => {
return resolve(data);
});
});
}
/**
* Unbinds an event listener.
*/
off(event, callback) {
this.removeListener(event, callback);
}
}