Amazon link shortener

amazon.js

javascript: (function () {
  let url = window.location.toString();
  let splitUrl = url.split("/");
  if (splitUrl[2].includes("amazon") && splitUrl[3] != "dp") {
      goodId = splitUrl[5].split("?")[0];
      window.location = "https://"+splitUrl[2] + "/dp/"+goodId;
  }
  else{
    alert("URL is already either minimized, or you're not on Amazon.");
  }
})();