jquery datatables 1.10 -check json at first

Question

I use jquery datatables

When my json is:

{"apps":
    {"app":
        [{"id":"1","user":"test"}]
    }
}

and DataTable works well

$('#getInfo')
    .DataTable(
            {
                "ajax" : {
                    "url" : "getinfo",
                    "dataSrc" : "apps.app"
                },
                "columns" : [
                        {
                            "data" : "id"
                        },
                        {
                            "data" : "user"
                        },
                ],

            });

But there could be a problem,the json could be null if backend get nothing.

{"apps":null} 

If in this situation, datatable will have problem````

console message show:

Uncaught TypeError: Cannot read property 'length' of undefined    

I want to check if datatable get nothing,alert a message to user
Please guide me thank you!

Answer 1

dataSrc can also be a function you can use to manipulate the JSON before items are injected, or in this case do something (as returning a valid empty object) if nothing is returned.

ajax: {
  url: "getinfo",
  dataSrc: function(json) {
    if (typeof json.apps == 'object') {
       return json.apps.app
    } else {
       return [{"id":"","user":""}]
    }
  }
}
...