This Tutorial on express js middleware will walk you through all the topics like what is middleware, function of middleware and then we will be creating a middleware in express js. Middleware is a request handler that has access to the application's request-response cycle. It is a function that contains the request object, response object, and the next middleware function, Middleware can only be applied using routes. With the help of middleware, we can access and modify request and response, and we use functions to modity our middleware to perform many tasks. We can create a middleware in a router files but the best way is to create a middleware file separately and then use it, Creating and using middleware is very easy.

2. What’s in it for you?
• What is Middleware?
• Functions of middleware
• Creating middleware in express

3. What is Middleware?
Middleware is a request handler that has access to the
application's request-response cycle. It is a function
which contains request object, response object and the
next middleware function
Middleware can send the response to server before
the request
Request
API
MIDDLEWARE
Response

4. Functions of middleware
Execute any code
Make changes to the
request response
objects
End the request-
response cycle
Call the next middleware
function in the stack