Konsep Integrasi JS dan CSS

 <style>

#hitam{

background-color: black;

width: 300px;

height: 300px;;

color: white;

}

</style>

<script>

function munculkan(){

var hitam = document.getElementById('hitam');

hitam.style.display = "block";

}

function sembunyikan(){

var hitam = document.getElementById('hitam');

hitam.style.display = "none";

}

</script>

<p>

<button onclick="sembunyikan()">Hide</button> <button onclick="munculkan()">

    Show

</button>

</p>

<div id="hitam"></div>