Node.js Event Loop

Node.js Event Loop

Node.js is a single-threaded event-driven platform that is capable of running non-blocking, asynchronously programming. 

it can support concurrency via the concept of event and callbacks.

The event loop allows Node.js to perform non-blocking I/O operations despite the fact that JavaScript is single-threaded.

Node.js Event Loop that listens for events, and then triggers a callback function when one of those events is detected.

The event loop executes tasks from the event queue only when the call stack is empty.

Syntax 

var events = require('events'); // import events module to handle events

var eventEmitter = new events.EventEmitter(); //Create an eventEmitter object

eventEmitter.on('eventName', eventHandler); // create event

eventEmitter.emit('eventName'); // fire event

Example :

// Import events module
var events = require('events');

// Create an eventEmitter object
var eventEmitter = new events.EventEmitter();

// Create an event handler as follows
var firstHandler = function connected() {
   console.log('Entered in first loop successfully.');
  
   // Fire the secondLoop event 
   eventEmitter.emit('secondLoop');
}

// Bind the connection event with the handler
eventEmitter.on('firstloop', firstHandler);
 
// Bind the secondEvent event with the anonymous function
eventEmitter.on('secondLoop', function(){
   console.log('Entered in second loop successfully.');
});

// Fire the firstloop event 
eventEmitter.emit('firstloop');

Output :

Entered in first loop successfully.
Entered in second loop successfully.