What are middlewares in Express.js?

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Middlewares in Express.js are functions that have access to the request (req), response (res), and the next() function in the application’s request-response cycle. They act as a pipeline where each middleware can process, modify, or terminate the request before passing control to the next middleware or route handler.

Middleware Function Signature:

Types of Middleware:

1. Application-level Middleware:
   Applied globally using app.use().

2. Route-level Middleware:
   Used for specific routes.

3. Error-handling Middleware:
   Handles errors in the app (uses 4 parameters).

4. Built-in Middleware:
   Provided by Express (e.g., express.static, express.json).

5. Third-party Middleware:
   Like morgan for logging or cors for enabling Cross-Origin Resource Sharing.

Why Use Middleware?

• Modularity: Break functionality into reusable units.

• Control: Process requests step-by-step.

• Reusability: Use the same middleware across routes.

• Security & Logging: Handle authentication, logging, validation, etc.

Conclusion:

Middle wares are a core concept in Express.js that allow developers to handle tasks such as authentication, logging, parsing, and error handling efficiently by chaining processing logic in a clean and maintainable way.

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