Question

I am trying to build a webapp that gets data from server and shows it to user. Script gets data from server every 10 seconds and if data has changed it alerts user. This is the code I’m using now, but it alerts every 10 second whether the data has changed or not.

So how do I need to alter my scipt to make it compare the old JSON and the new JSON and see if they are different, and if they are show alert before updating data shown to user?

$('#ListPage').bind('pageinit', function(event) {
    getList1();
});
setInterval ( "getList1()", 10000 );
var old = "";

function getEmployeeList1() {
    $.getJSON(serviceURL + 'getemployees.php?' + formArray, function(data) {
        if(data != old){ // data from the server is not same as old
            $('#nollalista li').remove();
            keikka = data.key;
            $.each(keikka, function(index, lista) {
                $('#nollalista').append('<li><a href="employeedetails.html?id=' + lista.IND + '">' +
                        '<h4>' + lista.OSO + '</h4>' +
                        '<p>' + lista.AIKA + '</p>' +'</a></li>');
            });
            $('#nollalista').listview('refresh');

            if(old != "")
                alert("New data!");        
            old = data;
        }
    });
}  

Answer 1

A very easy (but kind of lame) solution is comparing the string representations:

if(JSON.stringify(a) != JSON.stringify(b)) { ... }