Understand the functionality of the "next" parameter in Node.js Express middleware functions

Question

I'm working on Nodejs and using "Express js" and now I'm working on "Middleware Functions" and this is my current code

const express = require('express')
const app = express()

const myLogger = function (req, res, next) {
  console.log('LOGGED')
  next()
}

app.use(myLogger)

app.get('/', (req, res) => {
  res.send('Hello World!')
})

I'm confused about the "next" parameter and I have the following questions about the middleware function

1. What is the use of "next"? Is this a redirect to the "next middleware function"? What if so?
2. What happens if there is no "second middleware"?
3. What happens if we don't use "next"?
4. Can we redirect to custom middleware within "next"?

Answer 1

1. Yes, calling next is important as this allows express.js to move to the next middleware, otherwise it would be left dangling and the application would not work properly.

2) Your request will reach the route handler and you will receive a response containing the message "Hello World"

3) If you do not call next, the request will be terminated and the application will remain suspended

4) Yes, you can use next to redirect to a custom middleware function. Whenever next is called with arguments, expresss will treat it as an error message. You can define custom error handling middleware to direct it according to your needs.