Difference between app-level and route-level middleware in Express

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. In this article, we will go through app-level and route-level middleware and also see the key differences between them.

What is App-level Middleware?

App-level middleware, also known as application-level middleware, is configured on the utility degree using app.Use() or similar methods. It intercepts all incoming requests and executes code regardless of the particular course or path.

Characteristics:

• Global Reach: App-stage middleware applies to each request processed with the aid of the Express software.
• Initialization Order: Placed before route definitions, it executes in the order they’re defined inside the application.
• Common Use Cases: Logging, mistakes dealing with, authentication, placing headers, parsing requests, and serving static files.

Example:

Javascript

const express = require ('express')
const app = express ()
app.use ((req, res, next) => {
    console.log (‘App-level middleware’)
    next();
})

What is Route-Level Middleware?

Route-stage middleware is specific to sure routes or paths within an Express application. It’s described the usage of app.Use() or router.Use() and is invoked simplest while a request suits the defined direction.

Characteristics:

• Route-Specific: Applies to specific routes or a set of routes primarily based on route matching.
• Execution Order: Defined in proximity to specific routes, executing earlier than the path’s handler feature.
• Targeted Use Cases: Route authentication, input validation, course-specific logging, etc.

Example:

Javascript

const router = express.Router()
router.use((req, res, next) => {
      console.log('User router middleware');
      next();
});

Difference between the App-level and route-level middleware:

App-level middleware	route-level middleware
An intermediate implementation binds to an expression using app.use ()	Router level middleware works the same as application-level middleware, except that they depend on the express. Router () instance.
It is a universal and applicable to all methods globally.	The source of routing group or route is specific.
It is complete for all the applications except of route.	Only done when the specified path matches.
Small granular control for tasks that need to be implemented globally.	More control, ideal for certain tasks.
Applications have methods of listening and other methods.	Routers have no methods like this.
The application “does” the main role.	While routing only groups some routes and provides encapsulation.

Conclusion:

We have discuss all the key point about application level and route level middleware. In Express.js’ Middleware search, it is important to understand the difference between application middleware and middleware. The medium at the application level provides the general canvas for working on the method, while the medium at the route level provides the surgical precision for adjusting the work to a method. The art of using this medium is in the hands of the producer, who must know the difference, variation and effect of each method. As Express.js continues to evolve, knowledge of different editing frameworks has become an essential skill for building effective and efficient web applications . In future their will be more upgraded version of this technology.