Add ServerSentEvents.js example (#709) (#711)

examples/ServerSentEvents.js

@@ -0,0 +1,48 @@
+/* Server-sent events (EventSource) example */
+/* curl -n localhost:9001 # check events by using curl */
+
+const uWS = require('../dist/uws.js');
+const port = 9001;
+
+const headers = [
+  ['Content-Type', 'text/event-stream'],
+  ['Connection', 'keep-alive'],
+  ['Cache-Control', 'no-cache']
+]
+
+function sendHeaders(res) {
+  for (const [header, value] of headers) {
+    res.writeHeader(header, value)
+  }
+}
+
+function serializeData(data) {
+  return `data: ${JSON.stringify(data)}\n\n`
+}
+
+const app = uWS./*SSL*/App({
+  key_file_name: 'misc/key.pem',
+  cert_file_name: 'misc/cert.pem',
+  passphrase: '1234'
+}).get('/*', (res) => {
+  const clientId = Date.now()
+  console.log(`Client with id: ${clientId} connected, starting streaming`)
+  sendHeaders(res);
+  res.writeStatus('200 OK')
+
+  let intervalRef = setInterval(() => {
+    res.write(serializeData({ message: 'Hello world!' }))
+  }, 1000)
+
+  res.onAborted(() => {
+    clearInterval(intervalRef)
+    intervalRef = undefined
+    console.log(`Client with id: ${clientId} disconnected`)
+  })
+}).listen(port, (token) => {
+  if (token) {
+    console.log('Listening to port ' + port);
+  } else {
+    console.log('Failed to listen to port ' + port);
+  }
+});