JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="fulloptions" type="text" value=""></textarea>
<div id="alloptions">
    <ul>
        <li>
            <input type="checkbox" name="option1" value="Option1" />Test1</li>
        <li>
            <input type="checkbox" name="option1" value="Option2" />Test2</li>
        <li>
            <input type="checkbox" name="option1" value="Option3" />Test3</li>
    </ul>
</div>

JavaScript

var checkboxes = $("#alloptions li input[type='checkbox']");

checkboxes.on('change', function() {
    $('#fulloptions').val(
        checkboxes.filter(':checked').map(function(item) {
            return this.value;
        }).get().join(', ')
     );
});