title: What are React Native's caching behaviors for fetch
body: <p>What currently are React Native's default behaviors for caching in <code>fetch</code> calls? The official FB guides simply say "look at Mozilla!" but we're not on a web browser. I would assume cache behavior is custom here as result of the middleware.</p>
  
  <p>Let's say I do: <code>fetch("https://exampleserver.com/myfile.json")</code></p>
  
  <ul>
  <li><p>Are requests automatically cached once called?</p></li>
  <li><p>Is the request contents of <code>myfile.json</code> cached the entire "session" (ie: App is running active/bg, but not forced closed by user).</p>
  
  <ul>
  <li>Where is the request cached? Ie: is it using <code>AsyncStorage</code></li>
  <li>Would <code>fetch</code> the URL again result in the app reading cache.</li>
  <li>How "fast" is caching, if for some reason I have to instantly request <code>myfile.json</code> multiple times, is it going to basically ignore cache at that point and make all those separate calls? (I am seeing this behavior in debugger)</li>
  </ul></li>
  <li><p>When I force close the app, and reopen, does this cache still exist? </p>
  
  <ul>
  <li>If so, can I request the cache to persist?</li>
  </ul></li>
  <li><p>Any of this behavior different in iOS than Android? </p></li>
  <li><p>Does Expo affect this at all?</p></li>
  </ul>
  
  <p>Knowing at least some of this would help decide whether I need to write custom caching situation with AsyncStorage like so  <a href="https://gist.github.com/dslounge/18e555250a8df1f8218d702b21910eeb" rel="noreferrer">https://gist.github.com/dslounge/18e555250a8df1f8218d702b21910eeb</a></p>