[jQuery] processing json object

[JP]

how can I process values from json object without having to use
indivual reference names?

using json:

( {"Records": [ {"firstname":"Nancy","lastname":"Davolio"} ],
"RecordCount":"1" } )

instead of  :

$.ajax({ ......

    success: function(json, status) {
      if(json.Records){alert("Records="+json.Records[0].firstname );}
...

is there a way to numerically reference values --something like :

$.ajax({ ......

    success: function(json, status) {
      if(json.Records){alert("Records="+json.Records[0].0);}
...

only it should work :)

thanks in advance