javascript - AJAX and JS, Cannot read JSON data? -

i have following ajax code:

var ajax = new xmlhttprequest(); axaj.open("post", "index.php", true); ajax.setrequestheader("content-type", "application/x-www-form-urlencoded");  ajax.onreadystatechange = function(){     if(x.readystate == 4 && x.status == 200){         var returnval = ajax.responsetext;     } }  ajax.send("nextmax=-1"); 

and pairs php ends with:

echo json_encode(array(     'next_id' => $nextid ));  exit(); 

this works, is. if print out returnval inside ajax call, prints out correct array, correct value:

{"next_id":"935210077606657948"} 

but cannot access id directly. i've tried

var nextid = returnval.next_id; 

and

var nextid = returnval['next_id']; 

and other variations, return undefined.

how array elements within returnval?

thanks in advance.

found solution not 30 seconds after posting question. in same place:

switch

var returnval = ajax.responsetext; 

to

var returnval = json.parse(ajax.responsetext); 

and call works:

returnval.next_id;