JSFiddle - React, Tailwind, and code Playground

HTML

<select name="selectmenu1" id="selectmenu1">
                        <option value="o1">
                           a
                        </option>
                        <option value="o2">
                            b
                        </option>
                        <option value="o3">
                            c
                        </option>
                        <option value="o4">
                            d
                        </option>
                    </select>

JavaScript

$("#selectmenu1").change(function() {
    var selected = $(this).val();
    alert(selected);
});