JSFiddle - React, Tailwind, and code Playground

HTML

<div id="options">
<select id="optionOne">
<option>a</option>
<option>b</option>
</select>

    </div>

JavaScript

$(document).ready(function() {
    $('#optionOne').change(function (){
        if($(this).val() === 'b') {
            $('#options').append("<select><option>newset</option></select>");
        }            
    });
});