NJ-Events

Simple and light-weight event emitter library for JavaScript.

• No dependencies, less than 1KB pure JavaScript implementation.
• on method returns an ID. Use this ID to remove specific listener or the event-name to remove all the listeners.
• No aliases, just emit, on and off methods.

const emitter = new NJEvents();

const id = emitter.on('hey', data => {
  console.log(data);
});

emitter.emit('hey', 'how are you?');
emitter.off(id); 

Installation

npm install --save nj-events

You can use NJEvents as an ES6 module as follows:

import NJEvents from 'nj-events';

const emitter = new NJEvents();

Alertnatively you can include the script.js script before the closing </body> tag and then in your JS create a new instance of NJEvents as below.

<script src="path/to/script.js"></script>
<script>
    const emitter = new NJEvents();
</script>

Usage

NJ-Events are driven by the on, emit, off methods which are detailed below.

Registering an event

• on() - the listener is registered and will be active until removed explicitly.
• once() - the listener is removed after first trigger.
• both methods take an event_name:string, callback:function and an optional id:string as parameters.

const emitter = new NJEvents();

const id_on = emitter.on('hey', data => { // listener is registered until removed
  console.log(data);
});

const id_once = emitter.once('hey', data => { // listener is removed after first trigger
  console.log(data);
});

const custom_id = emitter.on('hey', data => { // init with custom id
  console.log(data);
}, YOUR_CUSTOM_ID);

Triggering an event

An event is triggered using the emit() by passing the event_name:string and data:any

emitter.emit('hey', 'how are you?');

Unregistering an event

An event can be unregistered using the off() with the below parameters

• event_name - any matching events and its listeners will be removed.
• id - event with the particular id will be removed, the event would still exist.

emitter.off('hey'); // unregister using event-name 
emitter.off(id); // unregister using the event ID

Releases and Changes

Check out the Releases and Change Logs for more information.

Copyright and License

The MIT license