gecko-dev/dom/websocket/tests/websocket_loadgroup_worker.js

onmessage = function(event) {
  if (event.data != 0) {
    var worker = new Worker("websocket_loadgroup_worker.js");
    worker.onmessage = function(e) {
      postMessage(e.data);
    };

    worker.postMessage(event.data - 1);
    return;
  }

  var ws = new WebSocket(
    "ws://mochi.test:8888/tests/dom/websocket/tests/file_websocket_hello"
  );
  ws.onopen = function(e) {
    postMessage("opened");
  };

  ws.onclose = function(e) {
    postMessage("closed");
  };

  ws.onerror = function(e) {
    postMessage("error");
  };
};