myDiv.style.display returns blank when set in master stylesheet

Question

Short Version: Is it standard behaviour that myDiv.style.display (Javascript) returns blank when I have set that div to display:none<

Answer 1

My solution:

Create class .hidden

.hidden {
   display: none !important;
}

Javascript:

function toggleHidden(id) {
    var x = document.getElementById(id);
    x.classList.toggle('hidden');
}