Node.js Event Emitter Explained in One Minute

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Yu-Ming, CHANG (he/him)
1 min readOct 3, 2022

What Is Event Emitter

Event Emitter is a class comes from default events package in Node environment. It is used to emit an event and to invoke a callback function when a certain event happens. It is just like how we manage event in browser JavaScript.

Why Use Event Emitter

Event Emitter is just a necessary class to implement Observer Pattern. Observer Pattern is the key, not event emitter. Wikipedia clearly explains the Observer Pattern that it aims to loose coupling our components so that they could become independent and makes them simpler and easier to manage.

How to Use Event Emitter

When to Use Event Emitter

When there is a need to notify a list of objects when a certain state is changed, we could choose to restructure our code to Observer Pattern to keep loose coupling.

Josedanielhq’s article, Observer Pattern for Dummies with JS, shows how to adopt Observer Pattern using YouTube as example. If you’re not familiar with Observer Pattern, you could give it a try.



Yu-Ming, CHANG (he/him)

I enjoy the positive mind flow when writing code to solve a problem. This is my journey to become a software developer, though now working as a product owner