JavaScript JavaScript: Adding a Function to Calculate the Sum of Product Quantities in Orders

[filipix]

Hello everyone!

I inherited an open-source program from an independent developer that manages receipts for local festivals. Among the various options, there is the so-called "digital order." Essentially, the receipts are sent from the computer to the local network, and through a web platform based on JavaScript and a website with CSS styles, the order is displayed in various departments.

I have a problem. I would like to insert a function into the JavaScript code that sounds simple to say but I find it difficult to implement: I want the SUM of the quantities of each product in the active orders to be displayed at the top of the page. Once I make the order disappear with the appropriate button, it is obviously canceled.

I'm attaching an image of the interface, and below I'm posting the part of the code that, from my limited knowledge, I believe is related to the part I want to modify.

Thanks to anyone willing to help me with this endeavor!

var lastLoad;
var orderK;
var tmrAnn;

$(document)
    .ready(function () {
        $('input[type="checkbox"]')
            .click(function () {
                if ($(this).prop("checked"))
                    {
                        $.post("/null", 'act=a_prstse&idticketl=' + $(this).attr('value'));
                        $(this).closest("tr").find(".cassa-sts-blue").removeClass("cassa-sts-blue").addClass("cassa-sts-green");
                        $(this).closest("tr").find(".fa-clock-o").removeClass("fa-clock-o").addClass("fa-check");
                    }
                else
                    {
                        $.post("/null", 'act=a_prstsp&idticketl=' + $(this).attr('value'));
                        $(this).closest("tr").find(".cassa-sts-green").removeClass("cassa-sts-green").addClass("cassa-sts-blue");
                        $(this).closest("tr").find(".fa-check").removeClass("fa-check").addClass("fa-clock-o");
                    }
            });
            
        lastLoad = $('#timestamp').attr('value');
        orderK = $('#orderk').attr('value');
        getAlert();
    });

function getAlert() {
    clearInterval(tmrAnn);
    //if (orderK.length > 0) {
        $.get("/orderka.html", {timestamp: lastLoad, orderknr: orderK, now: $.now()}).done(function (data) {
            if (data.indexOf("true") > -1) {location.reload(true);}
        });
        tmrAnn = setInterval(getAlert, 7000);
    //}
}

function reload() {
    location.reload(true);
}

function getInput(name, id, page) {
    var key = '#' + id + ' input[type=text]';
    var page = '/' + page;
    var allData = '';
    $(key).each(function () {
        allData += '&' + $(this).attr('name') + '=' + $(this).val();
    });   
    data = 'act=' + name + '&id=' + id + allData;
    $.post(page, data);
    return false;
}
    
function blinker () {
    $('.blink_me').fadeOut(700).fadeIn(700);
}

setInterval(blinker, 2500);