tbtlr/index.html

## index.html
<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
  </head>
  <body>
    <script type="application/javascript;version=1.7">
      var worker = new Worker('worker.js');
      var g;

      worker.onmessage = function (e) {
        g.send(e.data);
      };

      function fibonacci(num) {
        // Fibonacci code shameless copied from https://gist.github.com/986590. Thanks!
        worker.postMessage('(function(n){for(var a=0,b=1;n--;)b=a+(a=b);return a}(' + num + '))');
      }
      function sleep(ms) {
        worker.postMessage('var n=+new Date;while(+new Date-n<' + ms + ');');
      }

      function main() {
        console.log('Calculating fibonacci of 40...');
        var f = yield fibonacci(40);
        console.log('Done. Result: ' + f);

        console.log('Going to sleep for 5 seconds...');
        yield sleep(5000);
        console.log('Done.');

        yield;
      }

      g = main();
      g.next();
    </script>
  </body>
</html>

## worker.js
onmessage = function(e) {
  postMessage(eval(e.data));
}
	<!doctype html>
	<html>
	<head>
	<meta charset="utf-8">
	</head>
	<body>
	<script type="application/javascript;version=1.7">
	var worker = new Worker('worker.js');
	var g;

	worker.onmessage = function (e) {
	g.send(e.data);
	};

	function fibonacci(num) {
	// Fibonacci code shameless copied from https://gist.github.com/986590. Thanks!
	worker.postMessage('(function(n){for(var a=0,b=1;n--;)b=a+(a=b);return a}(' + num + '))');
	}
	function sleep(ms) {
	worker.postMessage('var n=+new Date;while(+new Date-n<' + ms + ');');
	}

	function main() {
	console.log('Calculating fibonacci of 40...');
	var f = yield fibonacci(40);
	console.log('Done. Result: ' + f);

	console.log('Going to sleep for 5 seconds...');
	yield sleep(5000);
	console.log('Done.');

	yield;
	}

	g = main();
	g.next();
	</script>
	</body>
	</html>