I'm not sure why you are stringifying the data if you want to manipulate it. So this will work:
var data = $("#vrsta_rada").select2("data");
$.each(data, function(key, value) {
var text = data[key].text
//or
var text = value.text
});
Is this what you are looking for? That will iterate through the list. I prefer to use data[key]
because you can then manipulate the data and it will change the original whereas value only makes a copy.