Parallel data fetching

parallelFetch.ts

/*  Parallel fetch
*   Case:   When you need to fetch data from server and 
*           those request does not need data from previous one (they are independent).
*   Pros:   Significantly reduces time to get whole response.
*/

type User = {}
type Organization = {}

declare function fetchUser(name: string): Promise<User>
declare function fetchOrganization(name: string): Promise<Organization>

async function fetchData(userName: string, organizationName: string) {
    const user = await fetchUser(userName);                 // fetches usualy ~300ms;
    const organization = await fetchUser(organizationName); // fetches usualy ~500ms;

    return { user, organization };                          // Overall fetching time will be ~800ms;
}

async function fetchData_(userName: string, organizationName: string) {
    const [user, organization] = await Promise.all([
        fetchUser(userName),           // fetches usualy ~300ms;
        fetchUser(organizationName),   // fetches usualy ~500ms;
    ]);

    return { user, organization };     // Overall fetching time will be ~500ms;
}