[Solved] Why does this interceptor cause a runtime error?intercept(context, next) { return next.handle().pipe(map(data => data.toUpperCase())); }Assuming data is an object. | NestJS

NestJS - Interceptors

Why does this interceptor cause a runtime error?

intercept(context, next) {
  return next.handle().pipe(map(data => data.toUpperCase()));
}

Assuming data is an object.

Apipe is not imported correctly

BtoUpperCase() is not a function on objects

Cnext.handle() returns a Promise, not Observable

Dcontext parameter is required to call toUpperCase()

Step-by-Step Solution

Solution:

Step 1: Understand data type in map
Data is an object, but toUpperCase() is a string method.
Step 2: Identify the error cause
Calling toUpperCase() on an object causes runtime error.
Final Answer:
toUpperCase() is not a function on objects -> Option B
Quick Check:
toUpperCase() only works on strings [OK]

Quick Trick: Check data type before calling string methods [OK]

Common Mistakes:

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Why does this interceptor cause a runtime error?