providers/.docs/content/2.essentials/2.fetchers.md

# Fetchers

When creating provider controls, it will need you to configure a fetcher.
This comes with some considerations depending on the environment youre running.

## Using `fetch()`
In most cases, you can use the `fetch()` API. This will work in newer versions of Node.js (18 and above) and on the browser.

```ts
const fetcher = makeStandardFetcher(fetch);
```

If you using older version of Node.js. You can use the npm package `node-fetch` to polyfill fetch:

```ts
import fetch from "node-fetch";

const fetcher = makeStandardFetcher(fetch);
```

## Using fetchers on the browser
When using this library on a browser, you will need a proxy. Browsers come with many restrictions on when a web request can be made, and to bypass those restrictions, you will need a cors proxy.

The movie-web team has a proxy pre-made and pre-configured for you to use. For more information, check out [movie-web/simple-proxy](https://github.com/movie-web/simple-proxy). After installing, you can use this proxy like so:

```ts
const fetcher = makeSimpleProxyFetcher("https://your.proxy.workers.dev/", fetch);
```

If you aren't able to use this specific proxy and need to use a different one, you can make your own fetcher in the next section.

## Making a derived fetcher

In some rare cases, a custom fetcher will need to be made. This can be quite difficult to do from scratch so it's recommended to base it off an existing fetcher and building your own functionality around it.

```ts
export function makeCustomFetcher(): Fetcher {
  const fetcher = makeStandardFetcher(f);
  const customFetcher: Fetcher = (url, ops) => {
    // Do something with the options and url here
    return fetcher(url, ops);
  };

  return customFetcher;
}
```

If you need to make your own fetcher for a proxy. Make sure you make it compatible with the following headers: `Set-Cookie`, `Cookie`, `Referer`, `Origin`. Proxied fetchers need to be able to write/read those headers when making a request.


## Making a fetcher from scratch

In some even rare cases, you need to make one completely from scratch.
This is the list of features it needs:
 - Send/read every header
 - Parse JSON, otherwise parse as text
 - Send JSON, Formdata or normal strings
 - get final destination url

It's not recommended to do this at all, but if you have to. You can base your code on the original implementation of `makeStandardFetcher`. Check the out [source code for it here](https://github.com/movie-web/providers/blob/dev/src/fetchers/standardFetch.ts).

Here is a basic template on how to make your own custom fetcher:

```ts
const myFetcher: Fetcher = (url, ops) => {
  // Do some fetching
  return {
    body: {},
    finalUrl: '',
    headers: new Headers(), // should only contain headers from ops.readHeaders
    statusCode: 200,
  };
}
```