JSFiddle - React, Tailwind, and code Playground

HTML

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

JavaScript

$('#save').click(function () {
    $('#mytable').find('tr').each(function () {
        var row = $(this);
        if (row.find('input[type="checkbox"]').is(':checked') &&
            row.find('textarea').val().length <= 0) {
            alert('You must fill the text area!');
        }
    });
});