JSFiddle - React, Tailwind, and code Playground

HTML

<form>

<select id="event_allDay" name="a">
   <option value="0" selected>No</option>
   <option value="1">Yes</option>
</select>
</form>
<button id="b">submit</button>

JavaScript

$('#b').click(function() {
    alert($('form').serialize());
});