JSFiddle - React, Tailwind, and code Playground

HTML

<select required>
    <option value="">Please select</option>
    <option>test</option>
    <option>test2</option>
    <option>test3</option>
</select>
<div id="error"></div>

CSS

select:invalid { border:5px solid red;}
select:valid {border: 5px solid green;}

JavaScript

$('select').change(function() {
    if($(this).is(':invalid')) {
        $('#error').html('invalid');
    } else {
        $('#error').html('valid');
    }
});