var wbl = {
    walutyContainer:$("#forexContainer"),
    getWaluty:function(){
        $.ajax({
            url: "application/walutyTabela.php",
            dataType: "json",
            type: "POST",
            async: false,
            success: function(response){
                wbl.walutyContainer.html(response['cont']);
            }
        })
    }
};
// do wywołania
wbl.getWaluty();
setInterval("wbl.getWaluty()", 20000);