JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.1.4.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" type="text/css" />
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/js-cookie/2.1.0/js.cookie.js"></script>
<div id="myModal" class="modal fade">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
                <h4 class="modal-title">Subscribe our Newsletter</h4>
            </div>
            <div class="modal-body">
                <img src="https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcRYXNLuN8M8-f0TZUM9DIiMD3bNN6B8hyvlyttFrUdN423bn7ZD">

            </div>
        </div>
    </div>
</div>

JavaScript

$(document).ready(function(){
            setTimeout(function(){
            if(!Cookies.get('modalShown')) {
            	$("#myModal").modal('show');
              Cookies.set('modalShown', true);
            } else {
            	alert('Your modal won\'t show again as it\'s shown before.');
            }
        			
    },3000);
 });