<div id="divid">
DIV element
</div>
<button onclick="checkHidden()">Check Hidden</button>
function checkHidden() {
var x = document.getElementById("divid");
if (window.getComputedStyle(x).display === "none") {
console.log("hidden");
}
else {
console.log("not hidden");
}
}
/*
run:
"not hidden"
*/