simplified ttd_dom_ready - does not support (old) IE

ttd_dom_ready.js

    (function (){
      window.ttd_dom_ready = window.ttd_dom_ready || function (cb) {
        if (document.readyState === "complete" ||
          (document.readyState !== "loading" && !document.documentElement.doScroll)) {
          cb();
        } else {
          let mcb = () => {
                document.removeEventListener("DOMContentLoaded", mcb);
                cb();
              };
          document.addEventListener("DOMContentLoaded", mcb);
        }
      }
    }());