## Data Fetching with WHATWG Fetch

There is isomorphic `core/fetch` module that can be used the same way in both
client-side and server-side code as follows:

```jsx
import fetch from '../core/fetch';

export const path = '/products';
export const action = async () => {
  const response = await fetch('/graphql?query={products{id,name}}');
  const data = await response.json();
  return <Layout><Products {...data} /></Layout>;
};
```

When this code executes on the client, the Ajax request will be sent via
GitHub's [fetch](https://github.com/github/fetch) library (`whatwg-fetch`),
that itself uses XHMLHttpRequest behind the scene unless `fetch` is supported
natively by the user's browser.

Whenever the same code executes on the server, it uses
[node-fetch](https://github.com/bitinn/node-fetch) module behind the scene that
itself sends an HTTP request via Node.js `http` module. It also converts
relative URLs to absolute (see `./core/fetch/fetch.server.js`).

Both `whatwg-fetch` and `node-fetch` modules have almost identical API. If
you're new to this API, the following article may give you a good introduction:

https://jakearchibald.com/2015/thats-so-fetch/