graphql-request.ts

// shared.ts

export const graphqlRequest = async <T>(
 query: string,
 variables = {},
): Promise<T> => {
 const headers = {
   ...buildContentTypeHeader('application/json'),
 };

 const body = JSON.stringify({
   query,
   variables: isNil(variables) || isEmpty(variables) ? null : variables,
 });

 return await fetch(createGraphqlUrl(), {
   method: 'POST',
   headers,
   body,
   credentials: 'same-origin',
 })
   .then((responseStream: any) => {
     return responseStream.json();
   })
   ...
};

...

// app.epic.ts

Const appDataInitializationQuery = `
  Query AppDataInitializationQuery {
    Products {
       ...
`

export const appDataInitializationEpic = (
  ...
): Observable<StoreAction> =>
 action$.pipe(
   ...
   asyncRequest(APP_DATA_INITIALIZATION_ASYNC, (action: StoreAction) => {
    return graphqlRequest(appDataInitializationQuery);
   }),
 );