JSFiddle - React, Tailwind, and code Playground

HTML

<select id="select">
    <option value="1">111</option>
    <option value="2">222</option>
    <option value="3">333</option>
</select>

<div id="warning" style="display:none">NO!!!</div>

JavaScript

$(function() {
    $('#select').change(function(){
        if ($(this).val() == "2") {
            $('#warning').show();
        } else {
            $('#warning').hide();
        }
    });
});