#68 Why we use app.use() in Node.js?

In Node.js with Express, app.use() is used to register middleware functions. It allows you to run code for every incoming request before it reaches a route or when matching a specific path.

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✅ Why We Use app.use():

1. Apply Middleware Globally

   app.use(express.json()); // parse incoming JSON requests
   

2. Serve Static Files

   app.use(express.static('public')); // serve HTML, CSS, JS from /public
   

3. Mount Middleware for Specific Paths

   app.use('/api', apiRoutes); // all routes inside apiRoutes will start with /api
   

4. Error Handling

   app.use((err, req, res, next) => {
     res.status(500).send('Something broke!');
   });
   

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🔁 Summary:

app.use() is a flexible way to plug in middleware or sub-routers, helping you handle requests, parse data, serve static files, and manage errors effectively.