JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
<script src="https://raw.githubusercontent.com/carhartl/jquery-cookie/master/src/jquery.cookie.js"></script>

JavaScript

var NAZWA_CIASTECZKA = 'xaxaxa'; // zmien jak chcesz potestować

function getCookie(cname) {
  var name = cname + "=";
  var ca = document.cookie.split(';');
  for (var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays * 24 * 60 * 60 * 1000));
  var expires = "expires=" + d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

$(document).ready(function() {  
  if (!$.cookie(NAZWA_CIASTECZKA)) {
    $.cookie(NAZWA_CIASTECZKA, 1, {expires: 7});
    window.setTimeout(function() {
      alert("DUPA"); // zamien na twoj popup
    }, 500);
  }
});