JSFiddle - React, Tailwind, and code Playground

HTML

<div class="b-container">
    Купон на скидку
    <button><a href="javascript:PopUpShow()">Открыть купон</a></button>
    <span class="k1">купон1</span>
</div>
<div class="b-popup" id="popup1">
    <div class="b-popup-content">
        Купон на скидку:
        купон1
    <a href="javascript:PopUpHide()">закрыть</a>
    </div>
</div>

CSS

*{
    font-family: Areal;
}
button {
  position:relative;
  z-index:2;
}
.k1 {
  position:relative;
  top:-35px;
  right:-105px;
  z-index:1;
  font-size:15px;
}
.b-container{
    width:200px;
    height:250px;
    background-color: #ccc;
    margin:0px auto;
    padding:10px;
    font-size:30px;
    color: #fff;
}
.b-popup{
    width:100%;
    min-height:100%;
    background-color: rgba(0,0,0,0.5);
    overflow:hidden;
    position:fixed;
    top:0px;
    z-index:3;
}
.b-popup .b-popup-content{
    margin:40px auto 0px auto;
    width:100px;
    height: 140px;
    padding:10px;
    background-color: #c5c5c5;
    border-radius:5px;
    box-shadow: 0px 0px 10px #000;
}

JavaScript

$(document).ready(function(){
    PopUpHide();
});
function PopUpShow(){
    $("#popup1").show();
}
function PopUpHide(){
    $("#popup1").hide();
}