1//elemento html
2<div id="myDIV"> </div>
3
4//funcionn js
5function myFunction() {
6    var x = document.getElementById("myDIV");
7    if (x.style.display === "none") {
8        x.style.display = "block";
9    } else {
10        x.style.display = "none";
11    }
12}