A simple event handling system for browser and node alike.
Install will npm or yarn:
npm install @jitesoft/events
yarn add @jitesoft/eventsThe event handler class is the main instance which handles listening and emitting of events.
The following methods are exposed on the event handler:
on(string: eventName, function: listener, number: priority = 0, boolean: once = false): number
The on method attaches a callback to the handler which will be fired once the given event is emitted by the handler.
It's possible to set a priority on the callback by changing the priority number value, where 0 is lowest priority. The once argument
determines if the callback should be removed after first run or not and defaults to false.
The method returns a handle id (number) which can be used to remove the event listener if wanted.
If the listener callback returns FALSE, the event will not bubble to the next handler.
once(string: eventName, function: listener, number: priority): number
The once method does pretty much the same as on, but is always a fire once listener type.
clear(): void
Clear empties all the listeners from the handler.
off(string: eventName, function|number: listener): boolean
The off method removes a given listener from the handler either by its handle or by passing its callback method.
emit(string: eventName, Event: event): void
Emits a event and fires each listener that listens to the given event.
emitAsync(string: eventName, Event: event, boolean: throw = false): Promise<void>
The emitAsync method works just like the Emit method, with the exception that it is an async method.
When used, it will group all the listeners by their priority and call them in batches, and just as with emit, if
one of the callback returns false, it will not call the next batch.
It uses the Promise.allSettled function - by default - which does not throw exceptions from the listeners.
If the throw parameter is passed, it will instead use all which will throw exceptions from the listeners.
When emitting a event, the Event class is used as a object which passes the data. It accepts a data object, which can be accessed
via the exposed data getter and an optional callee argument which can be used to pass information (or a reference) to the calling object.
The following example shows the most simple way create a handler and a listener and emit an event.
import { EventHandler, Event } from '@jitesoft/events';
const handler = new Handler();
handler.on('test-event', (event) => {
console.log(event.data.message);
});
handler.emit('test-event', new Event({
message: 'This is a simple example...'
}));MIT License
Copyright (c) 2018 Jitesoft
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