Express.js

Question 1

What is Express.js?

Answer 1

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for building web and mobile applications.

Question 2

True or False: Express.js is built on top of the Node.js HTTP module.

Answer 2

True

Question 3

Fill in the blank: Express.js uses ________ for routing.

Answer 3

middleware

Question 4

What is middleware in Express.js?

Answer 4

Middleware in Express.js is a function that has access to the request object, the response object, and the next middleware function in the application’s request-response cycle.

Question 5

How do you define a route in Express.js?

Answer 5

You define a route in Express.js using app.METHOD(path, handler), where METHOD is the HTTP method (GET, POST, etc.), path is the URL path, and handler is the callback function.

Question 6

What is the purpose of the ‘next’ function in middleware?

Answer 6

The ‘next’ function is used to pass control to the next middleware function in the stack. If not called, the request will be left hanging.

Question 7

What are the main advantages of using Express.js?

Answer 7

The main advantages of using Express.js include its lightweight nature, flexibility, extensive middleware support, and the ability to create RESTful APIs easily.

Question 8

True or False: Express.js can serve static files.

Answer 8

True

Question 9

What is the function of ‘app.use()’ in Express.js?

Answer 9

‘app.use()’ is used to mount middleware functions at a specified path. It can be used for serving static files, handling JSON requests, and more.

Question 10

What is the difference between app.get() and app.post()?

Answer 10

app.get() is used to handle GET requests, which retrieve data from the server, while app.post() is used to handle POST requests, which send data to the server.

Question 11

How can you handle errors in Express.js?

Answer 11

You can handle errors in Express.js by defining an error-handling middleware function with four arguments: err, req, res, and next.

Question 12

What is the purpose of the ‘body-parser’ middleware?

Answer 12

The ‘body-parser’ middleware is used to parse incoming request bodies in a middleware before your handlers, available under the req.body property.

Question 13

What does ‘res.send()’ do?

Answer 13

‘res.send()’ is used to send a response to the client, and it can send various types of responses, including strings, objects, and buffers.

Question 14

What is a route parameter in Express.js?

Answer 14

A route parameter is a placeholder in a route path that captures values from the URL, which can be accessed using req.params.

Question 15

How do you serve static files in Express.js?

Answer 15

You can serve static files in Express.js by using the ‘express.static’ middleware, which serves files from a specified directory.

Question 16

What is a RESTful API?

Answer 16

A RESTful API is an application programming interface that adheres to the principles of Representational State Transfer (REST), using standard HTTP methods and status codes.

Question 17

What is the purpose of the ‘cors’ middleware?

Answer 17

‘cors’ middleware is used to enable Cross-Origin Resource Sharing (CORS) in Express.js, allowing restricted resources on a web page to be requested from another domain.

Question 18

What are the common HTTP status codes used in Express.js?

Answer 18

Common HTTP status codes include 200 (OK), 201 (Created), 400 (Bad Request), 401 (Unauthorized), 404 (Not Found), and 500 (Internal Server Error).

Question 19

True or False: Express.js is only suitable for building web applications.

Answer 19

False

Question 20

What is the purpose of the ‘express.Router()’ method?

Answer 20

The ‘express.Router()’ method creates a new router object that can be used to define routes and middleware for a specific part of an application.

Question 21

How do you set the view engine in an Express.js application?

Answer 21

You set the view engine in an Express.js application by using ‘app.set(‘view engine’, ‘engineName’)’, where ‘engineName’ is the name of the templating engine.

Question 22

What is the function of ‘res.json()’?

Answer 22

‘res.json()’ is used to send a JSON response to the client, automatically setting the Content-Type header to application/json.

Question 23

How can you define a catch-all route in Express.js?

Answer 23

You can define a catch-all route in Express.js by placing a route handler at the end of your route definitions using app.get(‘*’, handler).

Question 24

What is the purpose of ‘app.listen()’?

Answer 24

‘app.listen()’ is used to bind and listen for connections on a specified host and port, effectively starting the Express server.