JSFiddle - React, Tailwind, and code Playground

HTML

<form id="test" name="test">
    <select name="dropdown" id="dropdown">
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3" selected="selected">3</option>
        <option value="4">4</option>
    </select>
</form>
<input type="hidden" value="" name="inputhidden" id="inputhidden" />

JavaScript

$('#dropdown').val($('inputhidden').val());