akirattii/app.js

## app.js
/*
0) start node app:
$ node app.js

1) start stream listening:
 browse to http://localhost:3000/

2) stop stream listening:
 browse to http://localhost:3000/stop
*/

var express = require('express');
var app = express();

// some data to response to a client:
const data = {
  $stop: false, // used to stop listening
  count: 0,
};

// client side html:
const html = `
  <html>
  <ul></ul>
  <script>
  var evtSource = new EventSource('/stream');
  var eventList = document.querySelector('ul');

  evtSource.onmessage = function(e) {
    var newElement = document.createElement("li");

    newElement.textContent = "message: " + e.data;
    eventList.appendChild(newElement);
  }
  </script>
  </html>`;

// first page
app.get('/', function(req, res) {
  res.send(html);
});

// stop listening
app.get('/stop', function(req, res) {
  _stopStream(data); // stop listening
  res.send(`[${req.path}] listening stopping`);
});

// listening start:
app.get('/stream',
  function(req, res, next) {
    console.log(`[${req.path}] listening starting`);
    _listenStream(req, res, data, (err) => {
      console.log(`[${req.path}] listening stopped`);
    });
  });


app.listen(3000, function() {
  console.log('Example app listening on port 3000!');
});


/**
 * @param responseData {Object} - Responsed to a client as JSON string of eventsource object.
 *
 * Spec:
 * If responseData.$stop === true, streaming listening is stopped.
 */
function _listenStream(req, res, responseData, cb) {
  // for SSE:
  const STATUS_OK = 200;
  // response header for sever-sent events
  const SSE_RESPONSE_HEADER = {
    'Connection': 'keep-alive',
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'X-Accel-Buffering': 'no'
  };
  // Interval of streaming loop
  const INTERVAL = 3000;
  // Writes response header.
  res.writeHead(STATUS_OK, SSE_RESPONSE_HEADER);

  // Interval loop:
  const intervalId = setInterval(() => {

    // TODO: Something to do if you need. It's up to you
    responseData.count += 1; // count up

    res.write(`data: ${JSON.stringify(responseData)}\n\n`);
    console.log("_listenStream: responseData:", responseData);
    if (responseData.$stop === true) {
      res.end();
      clearInterval(intervalId);
      responseData.$stop = false; // reset
    }
  }, INTERVAL);

  // first SSE response
  if (responseData.$stop !== true)
    res.write(`data: ${JSON.stringify(responseData)}\n\n`);

  req.on("close", function() {
    console.log("_listenStream: *** Close.");
  }).on("end", function() {
    console.log("_listenStream: *** End.");
    return cbexample && cb(null);
  });
}

function _stopStream(responseData) {
  //
  // If sets responseData.$stop = true, current listening is stopped...
  //
  responseData.$stop = true; // to stop streaming.
}

/* Console log:

$ node app.js
Example app listening on port 3000!
[/stream] listening starting
_listenStream: responseData: { '$stop': false, count: 1 }
_listenStream: responseData: { '$stop': true, count: 2 }
_listenStream: *** End.
[/stream] listening stopped
*/
	/*
	0) start node app:
	$ node app.js

	1) start stream listening:
	browse to http://localhost:3000/

	2) stop stream listening:
	browse to http://localhost:3000/stop
	*/

	var express = require('express');
	var app = express();

	// some data to response to a client:
	const data = {
	$stop: false, // used to stop listening
	count: 0,
	};

	// client side html:
	const html = `
	<html>
	<ul></ul>
	<script>
	var evtSource = new EventSource('/stream');
	var eventList = document.querySelector('ul');

	evtSource.onmessage = function(e) {
	var newElement = document.createElement("li");

	newElement.textContent = "message: " + e.data;
	eventList.appendChild(newElement);
	}
	</script>
	</html>`;

	// first page
	app.get('/', function(req, res) {
	res.send(html);
	});

	// stop listening
	app.get('/stop', function(req, res) {
	_stopStream(data); // stop listening
	res.send(`[${req.path}] listening stopping`);
	});

	// listening start:
	app.get('/stream',
	function(req, res, next) {
	console.log(`[${req.path}] listening starting`);
	_listenStream(req, res, data, (err) => {
	console.log(`[${req.path}] listening stopped`);
	});
	});


	app.listen(3000, function() {
	console.log('Example app listening on port 3000!');
	});


	/**
	* @param responseData {Object} - Responsed to a client as JSON string of eventsource object.
	*
	* Spec:
	* If responseData.$stop === true, streaming listening is stopped.
	*/
	function _listenStream(req, res, responseData, cb) {
	// for SSE:
	const STATUS_OK = 200;
	// response header for sever-sent events
	const SSE_RESPONSE_HEADER = {
	'Connection': 'keep-alive',
	'Content-Type': 'text/event-stream',
	'Cache-Control': 'no-cache',
	'X-Accel-Buffering': 'no'
	};
	// Interval of streaming loop
	const INTERVAL = 3000;
	// Writes response header.
	res.writeHead(STATUS_OK, SSE_RESPONSE_HEADER);

	// Interval loop:
	const intervalId = setInterval(() => {

	// TODO: Something to do if you need. It's up to you
	responseData.count += 1; // count up

	res.write(`data: ${JSON.stringify(responseData)}\n\n`);
	console.log("_listenStream: responseData:", responseData);
	if (responseData.$stop === true) {
	res.end();
	clearInterval(intervalId);
	responseData.$stop = false; // reset
	}
	}, INTERVAL);

	// first SSE response
	if (responseData.$stop !== true)
	res.write(`data: ${JSON.stringify(responseData)}\n\n`);

	req.on("close", function() {
	console.log("_listenStream: *** Close.");
	}).on("end", function() {
	console.log("_listenStream: *** End.");
	return cbexample && cb(null);
	});
	}

	function _stopStream(responseData) {
	//
	// If sets responseData.$stop = true, current listening is stopped...
	//
	responseData.$stop = true; // to stop streaming.
	}

	/* Console log:

	$ node app.js
	Example app listening on port 3000!
	[/stream] listening starting
	_listenStream: responseData: { '$stop': false, count: 1 }
	_listenStream: responseData: { '$stop': true, count: 2 }
	_listenStream: *** End.
	[/stream] listening stopped
	*/