NestJS - Middleware
You want to create a functional middleware that adds a custom header 'X-App-Version' with value '1.0' to every response. Which code correctly implements this?
You want to create a functional middleware that adds a custom header 'X-App-Version' with value '1.0' to every response. Which code correctly implements this?
hard📝 Application Q15 of 15
Step-by-Step Solution
Solution:
Step 1: Confirm middleware signature and header setting
Middleware must accept (req, res, next) and call next() after setting headers. res.setHeader is correct method.Step 2: Evaluate options
function addVersion(req, res, next) { res.setHeader('X-App-Version', '1.0'); next(); } sets header then calls next() correctly. function addVersion(req, res) { res.setHeader('X-App-Version', '1.0'); } misses next parameter and call. function addVersion(req, res, next) { next(); res.setHeader('X-App-Version', '1.0'); } calls next() before setting header, so header may not be sent. function addVersion(req, res, next) { req.setHeader('X-App-Version', '1.0'); next(); } uses req.setHeader which is incorrect because req cannot set response headers.Final Answer:
function addVersion(req, res, next) { res.setHeader('X-App-Version', '1.0'); next(); } -> Option AQuick Check:
Set header before next() with correct method [OK]
Quick Trick: Set header before next() using res.setHeader [OK]
Common Mistakes:
- Calling next() before setting headers
- Omitting next parameter or call
- Confusing req and res when setting headers
Master "Middleware" in NestJS
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