Javascript Açılır Kapanır Metin

<p id="demo"><br></p>
<center>
<button type="button" onclick='document.getElementById("demo").innerHTML = "<br>"'>Kapa</button>

<button type="button" onclick='document.getElementById("demo").innerHTML = "<div>Metin</div>"'>Aç</button></center>
<style>div {border-radius:4px; background-color:black; color:white; font-family:arial; text-align:center;}
button {background-color:white; outline:0; border:2px solid blue; border-radius:4px;}button:hover {border:2px solid lightblue;}
</style>