[Solved] Examine this Express error handler: app.use((err, req, res) => { res.status(500).json({ error: err.message }); }); What is the issue with this middleware? | Node.js

Node.js - Error Handling Patterns

Examine this Express error handler:

app.use((err, req, res) => {
  res.status(500).json({ error: err.message });
});

What is the issue with this middleware?

AIt lacks the 'next' parameter, so Express won't recognize it as error middleware.

BIt should use res.send() instead of res.json() for errors.

CIt should not set status code inside error middleware.

DIt should be registered before route handlers.

Step-by-Step Solution

Solution:

Step 1: Check middleware signature
Error handling middleware must have four parameters: err, req, res, next.
Step 2: Identify missing parameter
This middleware only has three parameters, missing 'next'.
Step 3: Understand Express behavior
Without 'next', Express treats it as normal middleware, not error handler.
Final Answer:
Missing 'next' parameter causes Express to ignore it as error handler. -> Option A
Quick Check:
Four parameters needed for error middleware [OK]

Quick Trick: Error middleware must have 4 parameters including 'next' [OK]

Common Mistakes:

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