3/17/2023 0 Comments Nodejs eventemitter![]() ![]() The output in the console will be as follows: an event occurred! When the event ‘eventOne’ is emitted, both the above callbacks should be invoked. MyEmitter.on('eventOne', c2) // Register for eventOne MyEmitter.on('eventOne', c1) // Register for eventOne Example 1 - Create an event emitter instance and register a couple of callbacks const myEmitter = new EventEmitter() Ĭonsole.log('yet another event occurred!') In fact, if you replace our EventEmitter with Node.js’s built-in ‘events’ module you will get the same result. Please note that our code will mimic the exact API of the Node.js ‘events’ module. The above basic features are sufficient to implement a full system using the eventing model.īefore we get into the coding, let’s take a look at how we will be using the EventEmitter class. What we will be building in this tutorial It’s kind of like a pub/sub or observer design pattern (though not exactly). Registering and unregistering listener functions.So, an emitter object basically has two main features: ![]() The concept is quite simple: emitter objects emit named events that cause previously registered listeners to be called. Many of Node’s built-in modules inherit from EventEmitter including prominent frameworks like Express.js. EventEmitter is at the core of Node asynchronous event-driven architecture. The EventEmitter is a module that facilitates communication/interaction between objects in Node. Event Emitters play a very important role in the Node.js ecosystem. You can check out my article All About Core Node.JS, for example.īut without further ado, let's get to the topic under discussion: “Event Emitters”. If you are new to Node.js there are many tutorials here on Medium and elsewhere. By Rajesh Pillai How to code your own event emitter in Node.js: a step-by-step guide Understand Node internals by coding small packages/modules Mastering the Node.JS Internals ![]()
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