JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a-opt">
    <table id="tabName">
        <tr>
            <td>
                <select id="a" name="a">
                    <option value="1">1</option>
                    <option value="2">2</option>
                    <option value="3">3</option>
                    <option value="4">4</option>
                </select>
            </td>
        </tr>
        <tr>
            <td colspan="2" style="background:transparent;"><input id="Add-btn" class="button" type="button" value="Add" /><span></span></td>
        </tr>
    </table>
</div>

JavaScript

$(document).ready(function() {
    $('#Add-btn').live('click',function() {
        $(document.body).append($("<div>"));
            var a = $('#a').val();
            $("#tabName tr:first").before("<tr><td class='greyed'><input type='hidden' name='added_a' value='" + a + "'>" + a + "</td><td style='background:transparent;'><input type='button' class='delete' value='Remove'></td></tr>");
            $("#a option:selected").attr("disabled", true);
    });
    $('#tabName td .delete').live('click',function() {
        // here I want to re-enable the select option ...removeAttr('disabled');
        $(this).parent().parent().remove(); 
        return false;
    });
});