Adding Middleware

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle.

Middleware functions can execute any code, make changes to res and req objects, end response cycle and call next middleware.

Very common example of middleware is cors module. To add CORS support, simply install it, require it and put this line:

app.use(cors());

before any routers or routing functions.