JSFiddle - React, Tailwind, and code Playground
HTML
<select>
<option >abc</option>
<option value='bcd'selected >bcd</option>
<option>abc</option>
<option >efg</option>
</select>
<div style='display:none;'>changed</div>
JavaScript
$(this).ready(function(){
$('select').change(function(){
if($(this).val() == 'bcd')
$('div').toggle();
});
$('select').trigger('change');
});