Express - Types of Middleware's

Question 1

What types of middleware are there in Express.js?

Answer 1

1. Application-level middleware
2. Router-level middleware
3. Error-handling middleware
4. Built-in middleware
5. Third-party middleware

Question 2

What is the difference between application-level & route-level middleware?

Answer 2

Application-level applies globally to all incoming requests and middleware applies only to specific routes.

Question 3

What is error handling middleware and how to implement it?

Answer 3

app.use(err, req, res,next)

Using the err parameter we can check for errors and handle them.

Question 4

If you have 5 middlewares, in which middleware will you do the error handling?

Answer 4

In the last middleware.

Question 5

What is built in middleware? How to serve static files from Express.js?

Answer 5

Built in middleware are functions provided by Express.js

app.use(express.static(‘/public’))

Question 6

What are third-party middlewares?

Answer 6

Middlewares we can install using npm install.

Examples helmet, body-parser, compression