JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<p>
    Total: <span id="total">0</span>
</p>

JavaScript

$('input[type=checkbox]').on('change', function () {
    $('#total').text(
        
        $('input[type=checkbox]:checked').length 
    );
});