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Node js events module

Events module provides EventEmitter class which is key to handle events and achieve the event driven architecture. EventEmitter object has two main functions
  • Emit a named event
  • Attach/Detach event listener to the event
Many core Node.js modules inherit the EventEmitter class. For example an http server emits event each time a user connects to it. fs emits an event when file is opened.

Here are the common methods from EventEmitter module:
  • addListener(): Add the specified listener
  • emit(): Call all the listeners registered with the specified name
  • on(): Add the specified listener
  • removeAllListeners(): Removes all listeners 
  • removeListener(): Removes the specified listener 

Example

Here is an example to emit and listen to an event.

main.js:
var events = require('events');

//create an object of EventEmitter 
var em = new events.EventEmitter();

//Subscribe for Event
em.on('Event', function (data) {
    console.log('Event subscriber: ' + data);
});

// Raising Event
em.emit('Event', 'This is Node.js event emitter example.');
Running the code:
PS C:\Users\mail2\Downloads\node-js-events-module> node main
Event subscriber: This is Node.js event emitter example.



Source Code:
https://github.com/it-code-lab/node-js-events-module


Next: Node.js modules

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