Express.js basics

Question 1

What are the advantages of using Express.js with Node.js?

Answer 1

Simplified web development, middleware support, flexible routing system, template engine integration.

Question 2

How to create an HTTP server using Express.js?

Answer 2

import {express} from “express”

const app = express();
const PORT = 3000;

app.listen(PORT, ()=>{console.log(“callback function”})

Question 3

What is middleware in Express.js and when to use them?

Answer 3

Middleware is a function that sits between the client and the application endpoints (get, post, put, delete, etc). It performs operations and passes control to the next middleware.

Request from client -> Pipeline of middlewares (logging, authentication, cors, etc) -> endpoint
Endpoint -> Response to client

Question 4

How to implement middleware in Express.js?

Answer 4

1. Define a middleware function (accepts 3 parameters: req, res, next)
2. Use app.use() to mount the middleware globally, meaning it will be executed for every incoming request to the application.
3. Start the server by listening on a specified port using app.listen().

Question 5

What is the purpose of the app.use() method in Express.js?

Answer 5

Used to mount middleware functions globally.

Question 6

What is the purpose of the next parameter in Express.js?

Answer 6

It’s a callback function used to pass control to the next middleware function in the stack.

Question 7

How to use middleware globally for a specific route?

Answer 7

app.use(‘/specific_route’, middleware)

Question 8

What is the request pipeline in Express?

Answer 8

All the steps that the request goes through until it reaches the endpoint.