EventBus

This class allows you to trigger and listen to events in JavaScript and TypeScript.

Table of contents

• Installation
  • Using NPM
  • Using <script> tag
• Usage
• Method reference
  • on()
  • off()
  • once()
  • trigger()

Installation

Using NPM

Install the latest stable version...

npm install --save @nestorrente/event-bus

... then import it in your modules:

import EventBus from '@nestorrente/event-bus';

Using <script> tag

You can download the latest version from here. Then, you can use it as any other JavaScript file:

<script src="event-bus.js"></script>

Or, if you prefer, you can use any of the following CDN repositories:

<!-- Unpkg -->
<script src="https://unpkg.com/@nestorrente/[email protected]"></script>

<!-- JsDelivr -->
<script src="https://cdn.jsdelivr.net/npm/@nestorrente/[email protected]"></script>

Usage

const eventBus = new EventBus();

eventBus.on('my-event', (param1, param2) => {
    console.log(`Event received with params "${param1}" and "${param2}"`);
});

eventBus.trigger('my-event', 1, 'two');
// console will display:
// > Event received with params "1" and "two"

// You can also chain method calls
eventBus.on('my-event', () => { /* do nothing */ })
        .trigger('my-event')
        .off('my-event');

Method reference

on()

on(event: string, listener: (...args: any[]) => void): EventBus;

Registers an event listener function for the specified event.

Usage example:

eventBus.on('my-event', (param1, param2, /* ... more params... */) => {
    // ... handle event...
});

off()

off(event: string, listener?: (...args: any[]) => void): EventBus;

Unregisters an event listener for the specified event.

If listener parameter is not specified, all event listeners registered for the specified event are unregistered.

Usage example:

// Define an event listener...
const myEventHandler = () => {
    console.log('Event triggered');
};

// ... register it on the bus...
eventBus.on('my-event', myEventHandler);

// ... then remove it
eventBus.off('my-event', myEventHandler);

// This will remove all registered event listeners for 'my-event'
eventBus.off('my-event');

once()

once(event: string, listener: (...args: any[]) => void): EventBus;

Registers an event listener function that will be called at most once for the specified event.

This method receives the same parameters as on().

Usage example:

eventBus.once('my-event', (param1, param2, /* ... more params... */) => {
    // ... handle event...
});

trigger()

trigger(event: string, ...eventParameters: any[]): EventBus;

Invokes all event listeners registered for the specified event. You can pass any number of parameters of any type.

Usage example:

// Without parameters
eventBus.trigger('my-event');

// With 4 parameters (number, boolean, string and array)
eventBus.trigger('my-event', 42, true, 'OMG', ['this', 'is', 'cool']);