JSFiddle - React, Tailwind, and code Playground

HTML

<p>(Disconnect your network temporarily and watch your Net tab if you want to really see things pile up.)</p>
<div id="reqs"></div>
<div id="req2"></div>

JavaScript

var n = 0, t = 0, u = 0, i, s = 'Stopping after 25 requests, to avoid killing jsfiddle’s server';
function a() {
    $.post('/ajax_html_echo/', function() {
        --n;
    });
    
    ++n; ++t;
    $('#reqs').html(n + ' a() requests in progress!');
    
    if(t > 25)
    {
        clearInterval(i);
        $('#reqs').html(s);
    }
}

function b() {
    ++u;
    $.post('/ajax_html_echo/', function() {
        $('#req2').html('b(): ' + new Date().toString());
        if(u <= 25)
        {
            setTimeout(b, 500);
        }
        else
        {
            $('#req2').html(s);
        }
    });
}

i = setInterval(a, 500);
setTimeout(b, 500);