emit.js

Efficient minimalist event emitter in JavaScript.

Installation

It is available with bower or npm:

bower install emit.js
npm install emit.js

Include emit.min.js to the HTML, and the emit object is now available in the global scope:

<script type="text/javascript" src="/path/to/bower_components/emit.js/dist/emit.min.js"></script>

Alternately, you can use a module manager to avoid global scoping:

var emit = require('emit.js');
// or es6 import
import emit from 'emit.js';

Usage

Create an event emitter

var emitter = emit();

Register listener on it

You can register a listener with on and once method. Listeners registered with once will be triggered only once.

emitter.on('event', function(...args) {
    // the args depends on the emit call

    console.log('I am a listener');
});

// you can also register an event with a regex
emitter.on(/^event(foo)?$/, function(...args) {
    // the args depends on the emit call

    console.log('I am a listener');
});

// you can also register an event with a callback for powerful listener
emitter.on(function(event) {
    return event.substr(0, 5) === 'hello'; // We want to match all event beginning with `hello`.
}, function(...args) {
    // the args depends on the emit call

    console.log('I am a listener');
});

emitter.once('event', function(...args) {
    console.log('I am triggered only once');
});

Unregister a listener

When you register a listener, you get in return a callback to unregister it:

var unregister = emitter.on('event', function(...args) {
    // the args depends on the emit call
    if (...) {
        unregister(); // unregistering this listener
    }

    console.log('I am a listener');
});

Emit an event

To emit an event, just use the emit method:

emitter.emit('event', arg1, arg2, ...); // we emit an event with as many parameters as we want

emitter.emit('event').then(function() {
    // all listeners have been called
}, function(error) {
    // an error occured
});

Removing all listeners

You can remove all listeners by calling the removeAllListeners method.

Development

Installation

make install

Build

make build or make build-dev (unminified version)

Watch

make watch

Test

make test

Contributing

All contributions are welcome and must pass the tests. If you add a new feature, please write tests for it.

License

This application is available under the MIT License.