The Power of Events: Mastering JavaScript’s Event Emitter Pattern

Supercharge Asynchronous Programming with Custom Event Handling

Photo by Greg Bulla on Unsplash

Beneath JavaScript’s single-threaded surface lies the ability to emit events for major state changes and lifecycle occurrences in our programs. By tapping into this event system through emitted custom events, we can unlock flexible non-blocking code!

Let’s examine how to leverage JavaScript’s core event emitter pattern to clean up callbacks and increase flexibility.

Events Fundamentals

At the core, an event is just a signal that some noteworthy action has occurred, like a click or keypress on a DOM element. We often register event listeners like:

button.addEventListener('click', handleClick);

These receive notification of that event type through the callback.

In Node.js and the browser we also have access to a base EventEmitter class that lets us define and dispatch events objects:

const ee = new EventEmitter();

ee.on('dataReceived', (data) => {
  // got data
});

ee.emit('dataReceived', {foo: 'bar'}); // dispatches event

By emitting named events and writing listeners for them, we unlock asynchronous, non-blocking…