Events in Node.js

What is an event in Node.js?

• An event in Node.js is an action or occurrence that can be detected and handled by the program.

• An event in Node.js is a function that runs automatically on startup.

• An event in Node.js is a method for creating new modules.

• An event in Node.js is a type of database query.

Can you name a type of custom event?

• Resize Event

• Scroll Event

• Hover Event

• Click Event

How do you create a custom event in Node.js?

• const EventEmitter = require('events'); const myEmitter = new EventEmitter(); myEmitter.on('eventName', () => { console.log('Event triggered!'); });

• const myEmitter = new EventEmitter(); myEmitter.on('eventName', console.log('An event occurred!'));

• const EventEmitter = require('events'); const myEmitter = new EventEmitter(); myEmitter.on('eventName', () => { console.log('An event occurred!'); }); myEmitter.emit('eventName');

• const myEmitter = new EventEmitter(); myEmitter.emit('eventName');

What is a listener in Node.js?

• A listener in Node.js is a function that handles events emitted by an EventEmitter.

• A listener is a type of database in Node.js.

• A listener is a command that executes scripts in Node.js.

• A listener is a built-in module for file handling in Node.js.

How do you add a listener to an event?

• element.attachEvent('eventType', callbackFunction);

• element.addListener('eventType', callbackFunction);

• element.on('eventType', callbackFunction);

• element.addEventListener('eventType', callbackFunction);

What happens when an event is emitted?

• The event is stored in a database.

• The event is logged for future reference.

• Listeners are triggered to execute their callbacks.

• The event is ignored and has no effect.

Can you remove a listener from an event?

• Yes, you can remove a listener from an event.

• Removing a listener is not supported in any event system.

• No, listeners cannot be removed from events.

• Listeners can only be added, not removed.

What is the purpose of the 'emit' method?

• To log data to the console.

• To create a new event listener.

• To trigger an event and send data to listeners.

• To remove an existing event listener.

How do you listen for a custom event?

• targetElement.listenFor('customEventName', callbackFunction);

• targetElement.addEvent('customEventName', callbackFunction);

• Use targetElement.addEventListener('customEventName', callbackFunction);

• Use targetElement.on('customEventName', callbackFunction);

What is the difference between a built-in event and a custom event?

• Built-in events are only used in web applications.

• Built-in events are predefined, while custom events are user-defined.

• Custom events cannot be predefined.

• Built-in events are always triggered by user actions.