XMLHttpRequest returns always undefined in IE9

Question

i would want to know for what reason this code works on firefox, chrome and IE10, but not in IE9

var ajaxReq = new XMLHttpRequest();
var params = "name="+$('#name').val()
var url = "register.php";

ajaxReq.open("POST", url, true);                               

ajaxReq.setRequestHeader("Content-type", "application/x-www-form-urlencoded");    
ajaxReq.setRequestHeader("Content-length",params.length);
ajaxReq.setRequestHeader("Connection", "close"); 

ajaxReq.onreadystatechange = function(){
 if(ajaxReq.readyState == 4 && ajaxReq.status == 200) 
{alert(ajaxReq.response)} //<---this results undefined

 }

The code contained in php file itself doesn't matters because for do some proofs i rent it very minimal:

header('Content-Type: text/json');
echo 'response';
exit;

Instead of .response, it should be .responseText or .responseXML - see HTTP response — andyb
– andyb, Commented Jun 3, 2013 at 8:30
wow it's worked! But can i use responseText in case i will receive JSON encode objects? — Sonia
– Sonia, Commented Jun 3, 2013 at 8:44
Yes, as JSON is a plain text format. I added this as an answer with a longer description. — andyb
– andyb, Commented Jun 3, 2013 at 8:51

andyb · Accepted Answer · 2013-06-03 08:54:18Z

5

Instead of .response, it should be .responseText or .responseXML - see HTTP response. In your case, I assume that changing to alert(ajaxReq.responseText); will fix it.

response is not a property of the XMLHttpRequest object, which is why the JavaScript engine is throwing an undefined error.

From the aforementioned documentation:

responseText will contain the response of the server in plain text by a conforming user agent

so use responseText for everything in plain text apart from XML, which includes JSON, as that is a plain text format.

edited Jun 3, 2013 at 8:54

answered Jun 3, 2013 at 8:47

andyb

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