Mark red label for finished message thread in facebook

FBMessageRedLabel.js

var doSetup = function () {
    if (document.querySelector('#q'))
        document.querySelector('#q').value = '[ATADI] initializing...';

    if (document.readyState != 'complete' || !document.querySelectorAll('._24tx').length) 
        return setTimeout(doSetup, 1e4);

    document.querySelector('._24tx').addEventListener('DOMSubtreeModified', function() {
        // console.log('DOMSubtreeModified');
        var inboxes = document.querySelectorAll('._24tx li');
        inboxes.forEach(function (inbox, idx) {
            var flag = inbox.querySelectorAll('._2fp8');
            var count = flag[0].innerText.trim();
            var html = flag[0].innerHTML.trim();
            // console.log(idx, count, html);
 
            if (!count && !~html.indexOf('repliedLast')) {
                inbox.setAttribute("style", "background-color:#ffcdd2;");
            }
        });
    }, false);

    if (document.querySelector('#q'))
        document.querySelector('#q').value = '[ATADI] setup completed';
}

window.onload = function () {
    
    if (document.querySelector('#q'))
        document.querySelector('#q').value = '[ATADI] window.onload';

    if (~window.location.pathname.indexOf('messages')) 
        return setTimeout(doSetup, 1e4);
}