JSFiddle - React, Tailwind, and code Playground
by Aakash Chakravarthy
HTML
<select multiple>
<optgroup label="Category 1">
<option value="dasd">Option 1...</option>
<option>Option 2...</option>
<option>Option 3...</option>
</optgroup>
<optgroup label="Category 2">
<option>Option 1...</option>
<option>Option 2...</option>
<option>Option 3...</option>
</optgroup>
<optgroup label="Category 3">
<option>Option 1...</option>
<option>Option 2...</option>
<option>Option 3...</option>
</optgroup>
</select>
<input type="text"/>
JavaScript
$('select').click(function(){
$('input').val($(this).val());
});