Cached Fetch GET Request

cachedFetchGet.js

/**
* CachedCall
*
* Caches a network GET request. When called more than once, the closure returns the cached value.
*
* @param {func}         asyncFunc - i.e. `async (arg) => {}`
* @param                ...args - spreads arguments into an array
* @return {Promise}    cachedResponse | unresolvedCall - thenable with a resolved value
*/
export const CachedCall = (asyncFunc, ...args) => {
  let cachedResponse;
  let callCount;
  let resolver;
  let unresolvedCall;

  return async () => {
    callCount = callCount ? callCount += 1 : 1;

    if (!cachedResponse && callCount === 1) {
      unresolvedCall = new Promise(resolve => (resolver = resolve));

      const res = await fetch(asyncFunc(...args));
      cachedResponse = await res.json();

      resolver(cachedResponse);

      return cachedResponse;
    }

    return unresolvedCall;
  };
};