Javascript: correctly display arrays data in the same row

I have two arrays that look like this:

var payments = {"items":[{"id_decoder":"1","mesi_pagati":"2"},{"id_decoder":"2","mesi_pagati":"1"}]}

var decoders = {"items":[{"id_decoder":"1","decoder":"decoder1","id_cliente":"1","username":"decoder1","password":"decoder1","note":"decoder1"},{"id_decoder":"2","decoder":"decoder2","id_cliente":"2","username":"decoder2","password":"decoder2","note":"decoder2"},{"id_decoder":"3","decoder":"decoder3","id_cliente":"3","username":"decoder3","password":"decoder3","note":"decoder3"},{"id_decoder":"4","decoder":"decoder4","id_cliente":"4","username":"decoder4","password":"decoder4","note":"decoder4"},{"id_decoder":"5","decoder":"decoder5","id_cliente":"5","username":"decoder5","password":"decoder5","note":"decoder5"},{"id_decoder":"6","decoder":"decoder6","id_cliente":"5","username":"decoder6","password":"decoder6","note":"decoder6"}]}

Select allOpen in new window

They are results coming from my database.
The 1st one is from payments table and the second one is from decoders table.

I want to write a row with all the following information in it:

all data coming from decoders and the total months that were not paid.

For this I can simply display in the right <span> the current month number (debts are calculated on a yearly base). If the id_decoder has payments then I want to subtract the payment number from the span number.

I've tried various approaches but I am not able to obtain the result I want.

The thing that came closer is:

function caricaUtentiGestioneUtenti() {
    var decoder;
    var pagamenti;

    $.getJSON(serviceURL + 'getdecoder.php', function (dati_decoder) {
        decoder = dati_decoder
        $.getJSON(serviceURL + 'getpagamenti.php', function (dati_pagamenti) {
            pagamenti = dati_pagamenti

            $.each(decoder, function (i, item) { // For each client
                console.log(decoder.items);

                item.pays = [];
                $.each(pagamenti, function (i, pay) { // Check each payment

                    /* COMMENTED SINCE THE DATA IS NOT YET OK
                $('#autocomplete_debitori').append('<li><a href="#popupPagamento" data-rel="popup" data-position-to="window" data-transition="flip">' +
                                '<p class="username">Username: <strong>'+ gruppi.username  +'</strong></p>'+
                                '<p class="password">Password: <strong>'+ gruppi.password  +'</strong></p>'+
                                '<p class="nome" id="'+ gruppi.nome  +'">Nome: <strong>'+ gruppi.nome  +'</strong></p>'+
                                '<p class="cognome" id="'+ gruppi.cognome  +'">Cognome: <strong>'+ gruppi.cognome  +'</strong></p>'+
                                '<p class="id_decoder" id="'+ gruppi.id_decoder +'">Decoder: <strong>'+ gruppi.nome_decoder  +'</strong></p>'+
                                '<p class="nome_gruppo">Gruppo: <strong>'+ gruppi.nome_gruppo  +'</strong></p>'+
                                '<p class="note">Note: <strong>'+ gruppi.note +'</strong></p>'+
                                '<span class="ui-li-count ui-li-count-f">'+ gruppi.MesiNonPagati +'</span>'+
                               '<a href="modifica_cliente.html"></a></a></li>');

        $('#autocomplete_debitori').trigger('create');
        $('#autocomplete_debitori').listview('refresh');
*/

                    if (item.id_decoder == pay.id_decoder) { // If matching ID
                        item.pays.push(pay); // Add it to this client
                    }

                });
            });
        });

    });
}

Select allOpen in new window

I'd appreciate hints and suggestions about how to do this properly (maybe I should just study better queries or enhance my for and while skills?): I am learning to program and every suggestion is very very welcome.

Thanks a lot to everyone for your time and patience.