Dead simple fetch caching

_Dead Simple Fetch Caching.md

Dead Simple Fetch Caching

Wrap fetch() in a memoize.

Not only does this cache repeated requests for the same resource, it also de-dupes concurrent requests!

Notes:

• Caching the raw response object doesn't work, since the response body is a stream and can thus only be read once
• Instead, cache your already read body (optionally still including the original request, just read the body prior)

cached-fetch.js

const CACHE = {};

const MAX_AGE = 60000;  // 1m

function cachedFetch(url, opts) {
  let cached = CACHE[url];
  if (cached && Date.now()-cached.time<MAX_AGE) return cached;
  
  let req = fetch(url, opts).then( r => r.json() );
  req.time = Date.now();

  // do fancy stuff

  return (CACHE[url] = req);
}

Great thanks for the idea, using a rewritten version of your code for CoOptimus-Enhanced-UX