Custom request handler

As shown above, the RequestService constructor takes a custom request handler as a parameter. Internal independence of RequestService from a fixed built-in request handler allows to handle requests of all sorts and environments (the browser or node) without locking in with a certain approach to handling requests.

Here's an example of a basic JSON request handler that can be passed to RequestService:

import {
    RequestHandler,
    RequestError,
    getRequestAction,
    toStringValueMap,
} from 'reqsrv';

const endpoint = 'https://api.example.com';

export const fetchJSON: RequestHandler = async (target, request) => {
    let {method, url} = getRequestAction({request, target, endpoint});

    let response = await fetch(url, {
        method,
        headers: toStringValueMap(request?.headers),
        body: request?.body ? JSON.stringify(request?.body) : null,
    });

    let {ok, status, statusText} = response;

    if (!ok) {
        throw new RequestError({
            status,
            statusText,
        });
    }

    try {
        return {
            ok,
            status,
            statusText,
            body: await response.json(),
        };
    }
    catch (error) {
        throw new RequestError(error);
    }
}

To meet the needs of a specific use case, the request handler's code can certainly depart from the example above (which is again the reason why it's not hardwired into the package).

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