JSFiddle - React, Tailwind, and code Playground

HTML

<table id="mytable">
    <tr>
        <td><input type="checkbox" /></td>
    </tr>
    <tr>
        <td><input type="checkbox" /></td>
    </tr>
    <tr>
        <td><input type="checkbox" /></td>
    </tr>
    <tr>
        <td><input type="checkbox" /></td>
    </tr>
</table>
<button id="save">Click</button>

JavaScript

$('#save').click(function () {
    alert($('#mytable').find('input[type="checkbox"]:checked').length + ' checked');
});