[Solved] What is wrong with this interceptor code snippet?intercept(req, next) { const modifiedReq = req.clone(); modifiedReq.headers.set('X-Custom', 'value'); return next.handle(modifiedReq); } | Angular

Angular - HTTP Client

What is wrong with this interceptor code snippet?

intercept(req, next) {
  const modifiedReq = req.clone();
  modifiedReq.headers.set('X-Custom', 'value');
  return next.handle(modifiedReq);
}

Anext.handle() must be called with original req

Bclone() must include headers explicitly to modify

CHeaders are immutable; set() does not change headers on cloned request

DInterceptor must return a Promise, not Observable

Step-by-Step Solution

Solution:

Step 1: Analyze header modification after cloning
Even after cloning, HttpHeaders are immutable; calling set() returns a new headers object but does not update the cloned request's headers.
Step 2: Correct way to modify headers
Headers must be set inside clone() options to update the request headers.
Final Answer:
Headers are immutable; set() does not change headers on cloned request -> Option C
Quick Check:
Modify headers inside clone() options [OK]

Quick Trick: Set headers inside clone() to update them [OK]

Common Mistakes:

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What is wrong with this interceptor code snippet?