JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://people.iola.dk/olau/flot/jquery.flot.js"></script>
<div class='change'>
    <div id="placeholder2" style="width:600px;"><select><option selected="selected">D</option><option>E</option></select></div>
<div id="placeholder" style="width:600px;"></div>

</div>

JavaScript

jQuery('.change').change(function(){
    
var testVar= jQuery('#placeholder2').val();

if (testVar == "D")
{
    var htmlString = '<select><option>C</option></select>'

jQuery('#placeholder').html(htmlString);
}else
{
    var htmlString = '<select><option>A</option><option>B</option></select>'

jQuery('#placeholder').html(htmlString);
}

    // more code here when I got the combination selection of those 2 inputs
    
});