If the request fails on the server or failed to reach the server due to network issues then HttpClient will return an error object instead of a successful reponse. In this case, you need to handle in the component by passing error object as a second callback to subscribe() method.
Let's see how it can be handled in the component with an example,
fetchUser() {
this.userService.getProfile()
.subscribe(
(data: User) => this.userProfile = { ...data }, // success path
error => this.error = error // error path
);
}
