JSFiddle - React, Tailwind, and code Playground
by kasperfish
HTML
<div id="header"></div>
<select id="selectid" name='name_of_select'>
<option value='on'>On</option>
<option value='off'>Off</option>
</select>
CSS
#header{
background:blue;
height:50px;
width:100%;
}
JavaScript
$('#selectid').on('change', function(){
if($(this).val()=='on'){
$('#header').fadeIn();
}
if($(this).val()=='off'){
$('#header').fadeOut();
}
});