A simple promise based cache for Authors

AuthorCache.js

class AuthorCache {
  cache = {};

  getAuthor(url) {
    // Returns a promise for
    let result = this.cache[url];
    if (result) {
      if (result.then) {
        // Request is already in flight, just return this promise, we don't need to do anything else
        console.debug("Request already in flight for ", url);
        return result;
      } else {
        // We already have the data, wrap it in a resolved promise so the component can't
        // tell the difference
        let promise = new Promise(function(resolve, reject) {
          resolve(result);
        });
        console.debug("Returning cached copy for ", url);
        return promise;
      }
    } else {
      // We don't have the data in the cache, we need to request it.
      let promise = fetch(url).then(res => res.json());
      console.debug("Fetching ", url);
      this.cache[url] = promise;
      promise.then(res => {
        // Replace the promise in the cache with the actual data we received
        this.cache[url] = res;
        return res;
      });
      return promise;
    }
  }
}

let authorCache = new AuthorCache();

export { authorCache };