Demonstration of need to synchronously define `onmessage` in web workers.

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
    <script src="script.js"></script>
  </head>

  <body>
    <h2>Check out the console - the worker's <code>onmessage</code> function will only be called for the second message.</h2>
  </body>

</html>

console.log('[main script] initializing worker');
var worker = new Worker('worker.js');
console.log('[main script] sending first message');
worker.postMessage('hello!');

setTimeout(function() {
  console.log('[main script] sending second message');
  worker.postMessage('second message');
}, 0);

/* Styles go here */

console.log('[worker] starting');

setTimeout(function() {
  console.log('[worker] assigning `onmessage`');

  onmessage = function(mesg) {
    console.log('[worker] received message: "' + mesg.data + '"');
  }
}, 0);