JSFiddle - React, Tailwind, and code Playground

HTML

<select id="selectbox">
    <option>Choose...</option>
    <optgroup label="Group A">
        <option>User 1</option>
        <option>User 2</option>
        <option>User 3</option>
    </optgroup>
    <optgroup label="Group B">
        <option>User 1</option>
        <option>User 2</option>
        <option>User 3</option>
    </optgroup>
</select>

JavaScript

$("#selectbox").on("change", function() {
    console.log("You have selected: " + $(this).val());
});