Run webworker from `file://`, with working `importScripts`

local-webworker.html

<script>

function createWebWorkerFromFunction(f) {
  var blobContents = ['(', f.toString(), ')();'];
  var blob = new Blob(blobContents, { type: 'application/javascript'});
  var blobUrl = URL.createObjectURL(blob);

  var worker = new Worker(blobUrl);
  URL.revokeObjectURL(blobUrl);

  return worker;
}

var worker = createWebWorkerFromFunction(function() {
  self.onmessage = function(e) {
    importScripts(e.data.scriptUrl);
  }
});

var workerUrl = (function() {
  var parts = document.location.href.split('/');
  parts[parts.length - 1] = 'worker.js';
  return parts.join('/');
}());

worker.onmessage = function(e) {
  console.log('main received message: ' + e.data);
}

// Send the worker the path to load the script from
worker.postMessage({ scriptUrl: workerUrl });

// Assuming worker.js has loaded the script and overwrote its `self.onmessage`
worker.postMessage('ping');
worker.postMessage('hello');

</script>

worker.js

onmessage = function(e) {
  console.log('worker received message: ' + e.data)
  if (e.data == 'ping') {
    postMessage('pong');
  } else {
    postMessage('unknown message');
  }
}