JSFiddle - React, Tailwind, and code Playground

HTML

<input type=checkbox id=Chckbox>
<br>
<div id=jlist>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
</div>

JavaScript

$(function(){
    i = $('#jlist li').size();
    console.log(i);
    
    function loopLi() {
        if ($('#Chckbox').not(":checked") ) {
            i++;
            $('<li>' + i + '</li>').appendTo('#jlist');
            setTimeout(loopLi,1000);
        }
    }
    loopLi();
});