In a REST API built with Express.js, you want to handle all unknown routes by returning a 404 JSON response with a message. Which middleware function correctly implements this?

hard📝 Application Q9 of 15

Rest API - HTTP Status Codes

Aapp.use((req, res) => { res.status(404).json({ error: 'Not Found' }); });

Bapp.get('*', (req, res) => { res.sendStatus(404); });

Capp.use((err, req, res, next) => { res.status(404).send('Not Found'); });

Dapp.all('*', (req, res) => { res.status(200).json({ error: 'Not Found' }); });

Step-by-Step Solution

Solution:

Step 1: Understand middleware for unknown routes
Middleware with app.use and no path catches all unmatched routes.
Step 2: Check correct status and JSON response
app.use((req, res) => { res.status(404).json({ error: 'Not Found' }); }); sets status 404 and sends JSON error message correctly.
Final Answer:
app.use((req, res) => { res.status(404).json({ error: 'Not Found' }); }); -> Option A
Quick Check:
Use app.use with res.status(404).json() for 404 middleware [OK]

Quick Trick: Use app.use with res.status(404).json() for 404 catch-all [OK]

Common Mistakes:

MISTAKES

Using app.get('*') which misses other methods
Sending 200 status with error message
Using error middleware for route not found

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In a REST API built with Express.js, you want to handle all unknown routes by returning a 404 JSON response with a message. Which middleware function correctly implements this?

Step 1: Understand middleware for unknown routes

Step 2: Check correct status and JSON response

Final Answer:

Quick Check:

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