test.js

//Файл api.js
const updateTickersWorker = new SharedWorker("../public/worker.js");

updateTickersWorker.port.start();

updateTickersWorker.port.onchange = function() {
  console.log("onchange posted to worker");
};

updateTickersWorker.port.onmessage = function(e) {
  console.log("Message received from worker", e);
};

updateTickersWorker.port.postMessage("hello shared web worker");

//Файл worker.js
onconnect = function(e) {
  const port = e.ports[0];

  port.addEventListener("message", function(e) {
    port.postMessage("hello from worker.js file");
  });

  port.postMessage("hellooo from worker.js file");

  port.start();
};