JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" name="tmp" value="" class="siska">siska
<input type="checkbox" name="tmp" value="" class="piska">piska
    <button>Show classnames:</button>
    <br>
<p></p>

JavaScript

function getClassName() {
    $( 'input[name="tmp"]:checked').each( function() {
            var class_name = $(this).attr("class");
            $('p').text(class_name);
    });
}

$('button').click( function() {
    getClassName();
});