JSFiddle - React, Tailwind, and code Playground

HTML

<select>
    <option value="1" selected data-original>repa</option>
    <option value="2">retek</option>
    <option value="3">mogyoro</option>
    <option value="4">rigo</option>
</select>
<button>clicky-clicky</button>

JavaScript

$(function(){
    $('button').click(function(){
        var $select = $('select');
        var original_value = null;
        var current_value = null;
        
        $select.find('option').each(function(){
            if ($(this).attr('selected')) {
                original_value = $(this).val();
            }
            if ($(this).prop('selected')) {
                current_value = $(this).val();
            }
        });
        alert('attr:' + original_value +' prop:' + current_value);
        
        // vagy sima js-el:
        var select = document.getElementsByTagName('select')[0];
        var options = select.getElementsByTagName('option');
        
        var selected_value = options[select.selectedIndex].value;
        var original_value = '';
        for (var i=0; i < options.length; ++i) {
            var option = options[i];
            if (option.hasAttribute('selected')) {
                original_value = option.value;
            }
        }
        alert('original:' + original_value + ' current:' +  current_value);
    });
});