rxjs-loading-state/dist/esm/track-loading-by.operator.js

Eliminates manual state management for loading and error states by transforming Observables into a LoadingState

import { Observable } from "rxjs";
/**
 * Tracks an observable, by emitting loading events to the passed in state machine
 * @param {LoadingStateMachine<Data>} loadingStateMachine
 */
export function trackLoadingBy(loadingStateMachine, mapper = (v) => v) {
    return function (source) {
        return new Observable((subscriber) => {
            loadingStateMachine.start();
            const innerSubscription = source.subscribe({
                next: (value) => {
                    loadingStateMachine.update(mapper(value));
                    subscriber.next(value);
                },
                error: (error) => {
                    loadingStateMachine.fail(error);
                    subscriber.error(error);
                },
                complete: () => {
                    loadingStateMachine.succeed(loadingStateMachine.data);
                    subscriber.complete();
                },
            });
            const tearDown = () => {
                innerSubscription.unsubscribe();
                // Reset to not-started if loading was cancelled
                if (loadingStateMachine.isLoading()) {
                    loadingStateMachine.reset();
                }
            };
            return tearDown;
        });
    };
}