mirror of
https://github.com/idanoo/GoScrobble.git
synced 2024-11-24 17:35:16 +00:00
53 lines
2.1 KiB
JavaScript
53 lines
2.1 KiB
JavaScript
|
/**
|
||
|
|
* @fileoverview A variant of EventEmitter which does not give listeners information about each other
|
||
|
|
* @author Teddy Katz
|
||
|
|
*/
|
||
|
|
|
||
|
|
"use strict";
|
||
|
|
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
// Typedefs
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
/**
|
||
|
|
* An event emitter
|
||
|
|
* @typedef {Object} SafeEmitter
|
||
|
|
* @property {function(eventName: string, listenerFunc: Function): void} on Adds a listener for a given event name
|
||
|
|
* @property {function(eventName: string, arg1?: any, arg2?: any, arg3?: any)} emit Emits an event with a given name.
|
||
|
|
* This calls all the listeners that were listening for that name, with `arg1`, `arg2`, and `arg3` as arguments.
|
||
|
|
* @property {function(): string[]} eventNames Gets the list of event names that have registered listeners.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Creates an object which can listen for and emit events.
|
||
|
|
* This is similar to the EventEmitter API in Node's standard library, but it has a few differences.
|
||
|
|
* The goal is to allow multiple modules to attach arbitrary listeners to the same emitter, without
|
||
|
|
* letting the modules know about each other at all.
|
||
|
|
* 1. It has no special keys like `error` and `newListener`, which would allow modules to detect when
|
||
|
|
* another module throws an error or registers a listener.
|
||
|
|
* 2. It calls listener functions without any `this` value. (`EventEmitter` calls listeners with a
|
||
|
|
* `this` value of the emitter instance, which would give listeners access to other listeners.)
|
||
|
|
* @returns {SafeEmitter} An emitter
|
||
|
|
*/
|
||
|
|
module.exports = () => {
|
||
|
|
const listeners = Object.create(null);
|
||
|
|
|
||
|
|
return Object.freeze({
|
||
|
|
on(eventName, listener) {
|
||
|
|
if (eventName in listeners) {
|
||
|
|
listeners[eventName].push(listener);
|
||
|
|
} else {
|
||
|
|
listeners[eventName] = [listener];
|
||
|
|
}
|
||
|
|
},
|
||
|
|
emit(eventName, ...args) {
|
||
|
|
if (eventName in listeners) {
|
||
|
|
listeners[eventName].forEach(listener => listener(...args));
|
||
|
|
}
|
||
|
|
},
|
||
|
|
eventNames() {
|
||
|
|
return Object.keys(listeners);
|
||
|
|
}
|
||
|
|
});
|
||
|
|
};
|