onclick(hide/show)
HTML
<div id="one"></div>
<div id="two"></div>
CSS
div {
width: 300px;
height: 200px;
background: red;
margin: 10px;
}
JavaScript
document.getElementById("one").onclick = function(){
if (document.getElementById("one").click) {
document.getElementById("two").style.display = "block";
}else {
document.getElementById("two").style.display = "none";
}
};
document.getElementById("two").style.display = "none";