1. function createWorker(f) {
    2.   var blob = new Blob(['(' + f.toString() +')()']);
    3.   var url = window.URL.createObjectURL(blob);
    4.   var worker = new Worker(url);
    5.   return worker;
    6. }
    8. var pollingWorker = createWorker(function (e) {
    9.   var cache;
    11.   function compare(new, old) { ... };
    13.   setInterval(function () {
    14.     fetch('/my-api-endpoint').then(function (res) {
    15.       var data = res.json();
    17.       if (!compare(data, cache)) {
    18.         cache = data;
    19.         self.postMessage(data);
    20.       }
    21.     })
    22.   }, 1000)
    23. });
    25. pollingWorker.onmessage = function () {
    26.   // render data
    27. }
    29. pollingWorker.postMessage('init');

    上面代码中，Worker 每秒钟轮询一次数据，然后跟缓存做比较。如果不一致，就说明服务端有了新的变化，因此就要通知主线程。

    https://www.ruanyifeng.com/blog/2018/07/web-worker.html

    https://developer.mozilla.org/zh-CN/docs/Web/API/Worker