Answers for "how element hidden"

html hidden

<!-- stops an element from rendering, but still loads it to memory-->
<p>this will show</p>
<p hidden>Thill will not show</p>

hide element

function replaceContentInContainer(target, source) {
  document.getElementById(target).innerHTML = document.getElementById(source).innerHTML;
}

function replaceContentInOtherContainer(replace_target, source) {
  document.getElementById(replace_target).innerHTML = document.getElementById(source).innerHTML;
}