backoff.ts

const backoff = (config?: { readonly scale?: number; readonly count?: number; }): readonly number[] => {
    return [...Array(config?.count ?? 4).keys()].map(item => 2 ** item * (config?.scale ?? 1));
}

const backoff$ = (config?: { readonly delay?: number; readonly count?: number; readonly scale?: number;}) => {
    return from([...Array(config?.count ?? 4).keys()]).pipe(
        concatMap(next => timer((config?.scale ?? 2) ** next * (config?.delay ?? 500)))
    )
}