document.addEventListener(
  "DOMContentLoaded",
  function() {
    // your code here
  },
  false
);

or;

function docReady(fn) {
  // see if DOM is already available
  if (document.readyState === "complete" || document.readyState === "interactive") {
    // call on next available tick
    setTimeout(fn, 1);
  } else {
    document.addEventListener("DOMContentLoaded", fn);
  }
}

console.dir(dom);