Writing a cookie with the current screen width

responsive.js

<script language="javascript">
  writeCookie();
  function writeCookie() {
    var today = new Date();
    var the_date = new Date("December 31, 2023");
    var the_cookie_date = the_date.toGMTString();
    var the_cookie = "screen="+ screen.width;
    var the_cookie = the_cookie + ";expires=" + the_cookie_date;
    document.cookie=the_cookie;
  }
</script>