# No build step

Run the host or client SDK in a browser with no build step. An import map tells the browser where
`@bitskiff/host` and `@bitskiff/client` are, so the import line is the same one a bundled app writes. This is the whole
page:

```html
<script type="importmap">
{
  "imports": {
    "@bitskiff/host": "https://docs.dev.bitskiff.com/sdk/host@0.3.0.js",
    "@bitskiff/host/unattended": "https://docs.dev.bitskiff.com/sdk/host@0.3.0/unattended.js",
    "@bitskiff/client": "https://docs.dev.bitskiff.com/sdk/client@0.3.0.js"
  },
  "integrity": {
    "https://docs.dev.bitskiff.com/sdk/host@0.3.0.js": "sha384-t4tevb6IaP3UssGRlkmHoQscYfON1BN2JyGY3zsoEGm3KmG2W3Mbe4icXcXQ7uGA",
    "https://docs.dev.bitskiff.com/sdk/host@0.3.0/unattended.js": "sha384-HEFX6nOFsYHXKEmBFo28v1a6kREAcKdfOPX7MKE8G8QAgiSpx2DfQy4VYs0KBgjA",
    "https://docs.dev.bitskiff.com/sdk/client@0.3.0.js": "sha384-d2cF/4NoPsVP5hrsmWr6yvH7578xCVoloemqaTxgXX6L5wd03MbZo1jrX1G0MJLa"
  }
}
</script>

<script type="module">
  import { BitskiffHost, qrSvg } from '@bitskiff/host';

  const host = new BitskiffHost({ key: 'bsk_pk_...' });
  host.channel('press').on('message', (m) => console.log(m.client.id, m.data));   // declare and listen

  const session = await host.open();                     // open last: it seals the channels
  document.body.innerHTML = qrSvg(session.joinCode.url);
</script>
```

## Module URLs

Copy the URL and the hash from the docs site of the environment you are shipping against. Each
module is built for one environment and talks only to that one. There is no `endpoint` option to
point it somewhere else.

The URLs above are this site's own. They were built for **dev** and talk
to `https://api.dev.bitskiff.com`. Each module carries its own package's version: the client
module's is the client package's, not the host's.

Two URLs serve each build:

- **The exact version**, `https://docs.dev.bitskiff.com/sdk/host@0.3.0.js`. It is never republished, so the code you
  tested is the code your page loads. Each URL in the map above is the exact version.
- **The line**, the same name with the patch number dropped. It is a one-line module that
  re-exports the newest release on that line, so it moves under you when that line releases again.
  The exact version it re-exports is still never republished.

The dev build is served at `https://docs.dev.bitskiff.com/sdk/host@dev.js`, and the other two files under the
same names with `@dev` in place of the version: `host@dev/unattended.js` and `client@dev.js`, which
a client page wants. None has a hash to pin. They change with every dev roll, so they are for
trying a change, never for a live app.

The line is the minor below 1.0 and the major from 1.0 on, because that is the axis a breaking
change crosses. Nothing wider than a line is served.

## The modules

Three modules are served, `@bitskiff/host`, `@bitskiff/host/unattended` and `@bitskiff/client`,
and all three are in the map above. The second is the `openForever` loop an unattended host runs,
a few kilobytes that take the host you already made as an argument: see
[Unattended hosts](/docs/guides/unattended-hosts/). The third is the client SDK: a client page
carries the same map and imports `BitskiffClient` from `@bitskiff/client`, with no build step
either. See [Client pages](/docs/guides/client-page/).

## Version and integrity

- **Ship the exact-version URL.** Keep the line URL for a scratch page. A page you ship pins the
  version it was tested against.
- **Keep the `integrity` entry in the import map.** The browser refuses to run a module whose hash
  does not match, which is what makes it safe to load code from another origin on a page that
  holds your key. A bare `import` from a URL has nowhere to put an integrity attribute, so the map
  is where the hash goes. The line URL has no hash to pin, and the module it re-exports is fetched
  as a dependency that no integrity entry covers. That is the other reason a shipped page names the
  exact version.

## Next steps

- [Quickstart](/docs/quickstart/)
- [Channels](/docs/guides/channels/)
- [Lifecycle](/docs/guides/lifecycle/)