[Dilettante_Pro]

var src = {"cont":[{"type":"text"}],"name":[{"type":"text"}],"tedt":"sdf","cont3":[{"type":"всякая хрень"}]};
var i = 0;
for(var key in src) {
   if(i == 3) {alert(key+':'+ JSON.stringify(src[key]))};
    i++;
}