Basic or Custom Middleware Example in Express Js

• Let's create a basic example with custom middleware in an Express.js application.

• Project Structure: Create a project structure with the following directories and files:

    - my-express-app/

        - middlewares/

            - myMiddleware.js

        - routes/

            - index.js

        - app.js

        - package.json

• Middleware File (`myMiddleware.js`): Create a custom middleware file in the `middlewares` directory:

    // middlewares/myMiddleware.js

    const myMiddleware = (req, res, next) => {

        console.log('Custom Middleware executed!');

        next(); // Call the next middleware in the stack

    };

    module.exports = myMiddleware;

• Route File (`index.js`): Create a route file in the `routes` directory:

    // routes/index.js

    const express = require('express');

    const router = express.Router();

    router.get('/', (req, res) => {

        res.send('Hello from the index route!');

    });

    module.exports = router;

• Express App (`app.js`): Set up the Express.js application:

    // app.js

    const express = require('express');

    const myMiddleware = require('./middlewares/myMiddleware');

    const indexRoute = require('./routes/index');

    const app = express();

    const PORT = 3000;

    // Use the custom middleware for all routes

    app.use(myMiddleware);

    // Use the index route

    app.use('/', indexRoute);

    app.listen(PORT, () => {

        console.log(`Server is running on http://localhost:${PORT}`);

    });

• Run the Application: Run your application using the command:

    node app.js

• Visit `http://localhost:3000` in your browser, and you should see the message "Hello from the index route!" in the console. The custom middleware `myMiddleware` is executed before the route handler, demonstrating the middleware's role in the request-response cycle.

• This example showcases a basic Express.js application with custom middleware. The custom middleware logs a message to the console and then calls the next middleware in the stack, which is the route handler. Middleware functions provide a powerful mechanism for handling various tasks during the processing of incoming requests.