Property ‘throw’ does not exist on type ‘typeof observable’

Explanation:

The error message “property ‘throw’ does not exist on type ‘typeof observable'” typically occurs when attempting to use the ‘throw’ method on the ‘Observable’ class but is not recognized because it does not exist in the current version or configuration of the ‘Observable’ class.

Before RxJS version 6, the ‘Observable’ class had the ‘throw’ method which was used to create an observable that immediately throws an error. However, starting from version 6, this method has been removed.

To handle error scenarios in newer versions of RxJS, you can make use of the ‘throwError’ function from the ‘rxjs’ library. This function allows you to create an observable that emits an error immediately, similar to the previous ‘throw’ method. Here’s an example:

import { throwError } from 'rxjs';

const observable = throwError("An error occurred.");
observable.subscribe({
   next: (value) => console.log(value), // Won't be called since it immediately throws an error
   error: (err) => console.error("Error:", err) // Error callback will be called with the thrown error message
});
   

In the above example, we import the ‘throwError’ function from the ‘rxjs’ library. We then create an observable using this function and provide it with the error message as the argument. Next, we subscribe to the observable and provide it with an object containing two callback functions: ‘next’ and ‘error’. Since we used ‘throwError’, the ‘next’ callback won’t be called, and the ‘error’ callback will be invoked with the thrown error message.

By using ‘throwError’ instead of the previous ‘throw’ method, you can overcome the error message “property ‘throw’ does not exist on type ‘typeof observable'”.