Give the divider an attribute, ie: data-target=".group_20211006"
and add class to the post container, ie: class="blah group_20211006"
. After the filter changes, loop through each divider and check if there’s any visible post container with matching date value.
HTML
<!-- First Group -->
<div class="divider" data-target=".group_20211001">October 1, 2021</div>
<div class="post-1 group_20211001">...</div>
<div class="post-2 group_20211001">...</div>
<div class="post-3 group_20211001">...</div>
<!-- Second Group -->
<div class="divider" data-group=".group_20211006">October 6, 2021</div>
<div class="post-1 group_20211006">...</div>
<div class="post-2 group_20211006">...</div>
<div class="post-3 group_20211006">...</div>
jQuery
(function($){
$(document).ready(function(){
$(document.body).on('change', '.myfilter', function(){
$('div.divider').each(function(e, el){
if ( $($(el).attr('data-group')).is(':visible').length > 0 ) {
$(el).show();
} else {
$(el).hide();
}
});
});
});
})(jQuery)
I haven’t tested, but this should be the concept to make it work.