Error is when the request fails on the server or fails to reach the server due to network issues. In this condition, HttpClient returns an error object instead of a successful response. To resolve this issue, we must handle the component by passing the error object as a second callback to the subscribe() method.

See the following example to understand how we handle in the component:

1. fetchUser() {  
2.   this.userService.getProfile()  
3.     .subscribe(  
4.       (data: User) => this.userProfile = { …data }, // success path  
5.       error => this.error = error // error path  
6.     );  
7. }  

You can write an error message to give the user some meaningful feedback instead of displaying the raw error object returned from HttpClient.