Middleware Syntax

The basic syntax for the middleware functions is:

app.get(path, (req, res, next) => {}, (req, res) => {})

Middleware functions take 3 arguments: the request object, the response object, and the next function in the application’s request-response cycle, i.e., two objects and one function.

Middleware functions execute some code that can have side effects on the app and usually add information to the request or response objects. They are also capable of ending the cycle by sending a response when some condition is satisfied. If they don’t send the response when they are done, they start the execution of the next function in the stack. This triggers calling the 3rd argument, next().

The middle part (req,res,next)=>{} is the middleware function. Here we generally perform the actions required before the user is allowed to view the webpage or call the data and many other functions. So let us create our own middleware and see its uses.

Express serves as a routing and Middleware framework for handling the different routing of the webpage and it works between the request and response cycle.

Middleware gets executed after the server receives the request and before the controller actions send the response. Middleware has and access to the request object, responses object, and next, it can process the request before the server sends a response. An Express-based application is a series of middleware function calls. In this article, we will discuss what is middleware in express.js.