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docs: add server-sent events example #204

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29 changes: 29 additions & 0 deletions examples/with-server-sent-events/index.js
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const { join } = require('path');
const polka = require('polka');

const { PORT = 3000 } = process.env;
const dir = join(__dirname, 'public');
const assets = require('sirv')(dir);

polka()
.use(assets)
.get('/subscribe', (request, response) => {
// You should add 'access-control-allow-origin' for
// cross-origin requests. We don't here because localhost
response.writeHead(200, {
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive',
});

setInterval(() => {
response.write('data: ' + Date.now() + '\n\n');
}, 1e3);

request.on('close', () => {
response.end();
});
})
.listen(PORT, () => {
console.log(`> Running on http://localhost:${PORT}`);
});
9 changes: 9 additions & 0 deletions examples/with-server-sent-events/package.json
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@@ -0,0 +1,9 @@
{
"scripts": {
"start": "node index"
},
"dependencies": {
"polka": "latest",
"sirv": "latest"
}
}
33 changes: 33 additions & 0 deletions examples/with-server-sent-events/public/index.html
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@@ -0,0 +1,33 @@
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Polka | Server Sent Events</title>
</head>
<body>
<h1>Server Sent Events</h1>
<ul id="sse-list"></ul>

<script>
document.addEventListener('DOMContentLoaded', function () {
const list = document.getElementById('sse-list');
const src = new EventSource('/subscribe');

src.onopen = function () {
console.log('[sse] connected');
};

src.onmessage = function (event) {
console.log('[sse] message', event);
const li = document.createElement('li');
li.innerText = `server time: ${event.data}`;
list.appendChild(li);
};

src.onerror = function () {
console.log('[sse]: error!');
};
});
</script>
</body>
</html>
19 changes: 19 additions & 0 deletions examples/with-server-sent-events/readme.md
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# Example: Server-Sent Events

Small `polka` example demonstrating how to use [Server-Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events).

The `public` directory contains an `index.html` file managing the Event Source Web API to subscribe to Server-Sent Events.
This file is served by Polka as a static asset using [`sirv`](https://github.com/lukeed/sirv) middleware.

On the server-side, the `/subscribe` endpoint initiates the communication channel for events to be sent.

## Setup

```sh
$ npm install
$ npm start
```

## Usage

Open a browser to `localhost:3000` and Server-Sent Events will be automatically subscribed to.
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