Nodejs Totorial: Creating and Using Events

Nodejs makes it very easy for us to use events, and we’re not limited to a collection of predefined events, it has a built-in module that allows us create and emit our own events.

Let me show you how easy it is to use this module, first we have require the events module and create the event emitter:

var ev = require('events');
var emitter = new ev.EventEmitter();

Ok, now we’re ready to start creating the events. As an example I’m going to use an event that I named new user, let’s create its event listener:

emitter.on('new user', function(){
   console.log('A new user has connected.');
});

I’ve used the function on from the EventEmitter to add this event listener, it receives the event name and a callback function that executes once the event is triggered.

Now the application is already listening the new user event, this is how we can emit it:

emitter.emit('new user');

Simple right? All we have to do is to call the emit function passing the event name.

But what if we have to pass parameters when emitting the event? Optionally, you can also pass some arguments to the emit function if you need, then you just have to declare them on the callback function as well. Here’s an example:

emitter.on('new user', function(user){
   console.log('The user '+user+' has connected.');
});
 
emitter.emit('new user','user1');

That’s it guys! Thanks for reading, if you have any doubts please let me know in the comments.

Recommended for you

Express.js: How to Change the Default Port By default Express uses port 3000, but sometimes this port is already been used by another application, so you can either close the other application or change the port. In this short tutorial I'm going to show you how easy it is to change the port. First let's open the bin/www file and locate th...
Node.js: How to make POST Requests with JSON data In this post I'm going to show you how to work with POST requests, I'll give you an example as simple as possible. First I'll create the Nodejs app to receive the requests, then I'll show you how to make the requests from the frontend. We're going to be using Expressjs, it's a very popular npm pa...
Tutorial: Integrating AngularJS with NodeJS Integrating AngularJS with NodeJS I know this tutorial may seem a little bit too basic for a lot of you, but these are two of the most popular javascript frameworks at the moment, as a result of that there are lots of people just getting started with NodeJS and AngularJS, and it's a very common ...
Creating a NodeJS project with Express Express is one of the most popular npm packages out there, it's basically a NodeJS web application framework that provides lots of functionalities and helps you to manage everything and organize your app into MVC on the back-end, and it's very easy to get started with. To use Express you first ne...

Leave a Reply

Your email address will not be published. Required fields are marked *

Obs: Use the tag <pre lang="LANGUAGE"> to include code blocks to your comment.
Example: <pre lang="javascript"> console.log('Test'); </pre>