Question

When I call a URL via AJAX, which cookies does it read? Same goes for sessions.

Who actually runs the thread? Is it my default system browser, current one, some other entity?

Answer 1

This can be confusing, since it all happens ‘behind the scenes’. I found that, like any other Javascript, the browser loading the page is the one to run the AJAX code. Moreover – the same instance of the browser, meaning sessions can be used as well.

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I’ve run a bit of code to come to this conclusion. The following examples are in classic ASP.

Firstly, I have one file which writes these variables:

Response.Cookies("testing") = "One, Two, Three"
Session("testing") = "Forty One, Forty Two, Forty Three"

Next, one file to read them (and display result):

Cookie is: 
<%
Response.Write Request.Cookies("testing")
%>
<br>
Session is:
<%
Response.Write Session("testing")
%>

At last, one file to AJAXly call them:

<div id="result"></div>
<script type="text/javascript">
//Different browsers initiate ajax differently
try {var oXH = eval("new Active"+"X"+"Object('MSXML2.XMLHTTP')");}
catch(e) {var oXH = new XMLHttpRequest();}

//Call page that reads the cookie
oXH.open("GET","/testCookie.asp",true);
oXH.onreadystatechange = function(){
    if ((oXH.readyState != 4)||(oXH.status != 200))
        return true;
    else
    {
        document.getElementById("result").innerHTML = oXH.responseText;
    }
};
oXH.send(null);
</script>

Running the first file on one browser and the last on a few, the first one shows:

Cookie is: One, Two, Three
Session is: Forty One, Forty Two, Forty Three

The rest display:

Cookie is:
Session is:

So there you have it 🙂