web-workers/simple-shared-worker/multiply.js

const first = document.querySelector("#number1");
const second = document.querySelector("#number2");

const result1 = document.querySelector(".result1");

if (!!window.SharedWorker) {
  const myWorker = new SharedWorker("worker.js");

  [first, second].forEach((input) => {
    input.onchange = () => {
      myWorker.port.postMessage([first.value, second.value]);
      console.log("Message posted to worker");
    };
  });

  myWorker.port.onmessage = (e) => {
    result1.textContent = e.data;
    console.log("Message received from worker");
    console.log(e.lastEventId);
  };
}