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What are functional HTTP Interceptors in modern Angular, and how do you register them?

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01

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Describe modern functional HTTP interceptors and registration.

httpinterceptors
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03

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Functional HTTP interceptors are lightweight functions of type HttpInterceptorFn. Instead of a class, they take req and next and return an Observable. They are registered via provideHttpClient(withInterceptors([myInterceptorFn])) in the application root config.

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An auth-token functional interceptor
import { HttpInterceptorFn, HttpRequest, HttpHandlerFn } from '@angular/common/http';
import { inject } from '@angular/core';
import { AuthService } from './auth.service';

export const authInterceptor: HttpInterceptorFn = (req: HttpRequest<unknown>, next: HttpHandlerFn) => {
  const token = inject(AuthService).getToken();

  if (token) {
    const clonedReq = req.clone({
      headers: req.headers.set('Authorization', 'Bearer ' + token)
    });
    return next(clonedReq);
  }

  return next(req);
};
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