Node.js – Events Module

Node.js – Events Module

Node.js is built on an event-driven architecture, making it highly efficient and suitable for asynchronous programming. The events module enables Node.js to create, handle, and respond to custom events, similar to event listeners in browser JavaScript.

This module is part of the Node.js core—no installation needed.

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Why Use the events Module?

• Emit and listen to custom application events
• Build loosely coupled, modular systems
• Cleanly handle asynchronous logic
• Backbone of core Node.js modules like http, net, fs, and stream

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Importing the Events Module

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Creating an Event Emitter

You can now use emitter to emit and listen for events.

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1. Listening to an Event using .on()

.on(eventName, callback) registers a listener. .emit(eventName) triggers the event.

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2. Passing Data with Events

You can pass multiple arguments to listeners if needed.

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3. Using .once() for One-Time Listeners

Use for setup or one-time tasks.

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4. Removing Event Listeners

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5. Counting Listeners

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6. EventEmitter in a Custom Class

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Real-World Use Case: HTTP Server Events

In this example, every request triggers the request event.

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Key Takeaways

• The events module supports custom event handling in Node.js
• EventEmitter is used to emit and listen to events
• Use .on(), .emit(), .once(), .off() for event workflows
• Useful for building asynchronous, modular applications