JSFiddle - React, Tailwind, and code Playground

HTML

<div class = "mobmeni">
  <div class = "mobmenidiv">
    <button id="kopceddown" class="mobmenikopce">click</button>
  </div>
</div>

<ul id = "mobddown">
  <li><a href="#">Берово</a></li>
  <li><a href="#">Берово</a></li>
  <li><a href="#">Берово</a></li>
  <li><a href="#">Берово</a></li>
</ul>

CSS

#mobddown{
    font-size: 2em;
    display: none;
}

#mobddown li{
    display: block;
    margin: 0;
    padding: 0.4em;
}

#mobddown li a{
    text-decoration: none;
    color: black;
}

#mobddown li:hover{
    background-color: #35aa96;
}

JavaScript

function show_or_hide()
    {
    	var ddown = document.getElementById("mobddown");
      if(ddown.style.display === "block")
        ddown.style.display = "none";
      else 
        ddown.style.display = "block";
    }

document.getElementById("kopceddown").addEventListener("click", show_or_hide);