Creating Custom Middlewares

Now that we have seen the different types of middlewares in Node.js, the next step is to learn how to create our own custom middlewares. Custom middlewares allow us to add specific functionalities to our application according to our needs.

How to Create a Custom Middleware

A custom middleware in Express is a function that has access to the request, response objects, and the next middleware function in the request/response cycle. To create a custom middleware, we simply define this function and use app.use to integrate it into our application.

Basic Structure

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Example: Request Logging Middleware

Let's create a custom middleware that logs details about each incoming request, such as the request method and URL.

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In this example, the requestLogging middleware is executed for each request that arrives at the server, logging the request method and URL before passing control to the next middleware or route handler.

Example: Basic Authentication Middleware

We will create a custom middleware to check if the user is authenticated before allowing access to certain routes.

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In this example, the checkAuthentication middleware is checked before allowing access to the /private route. If the user is not authenticated, an error response is sent; otherwise, the request will be handled normally.

[Insert image here: Diagram showing the flow of creation and execution of a custom middleware, from its definition to its application in the request.]

Now that you know how to create custom middlewares, you will be able to add specific and tailored functionalities according to your application's requirements. In the next module, we will see how to handle errors efficiently using error handling middlewares.