<!DOCTYPE html>
<html>
<head>
<title>Web Worker postMessage example</title>
</head>
<body>
<script>
const worker = new Worker( 'worker.js' );
worker.addEventListener( 'mycustomevent', console.log );
const event = new CustomEvent( 'mycustomevent' );
worker.dispatchEvent( event );
</script>
</body>
</html>
self.addEventListener( 'mycustomevent', console.log );