XMLHttpRequest to string

Question

I'm trying to make a function that sends an XMLHttpRequest and return a string with the contents of the response, but it always returns null. How do I fix this?

Code:

function getPage() {
    if (window.XMLHttpRequest)
    {
        xmlhttp=new XMLHttpRequest();
    }
    else
    {
        xmlhttp=new ActiveXObject('Microsoft.XMLHTTP');
    }
    xmlhttp.open('GET','page.php',false);
    xmlhttp.send();
    xmlDoc = xmlhttp.responseXML;
    if ($.browser.msie) return xmlDoc.xml;
    else return (new XMLSerializer()).serializeToString(xmlDoc);
}

Question 1: What browser are you using? There are two different code paths. Question 2: Since it seems you're using JQuery, why not use $.get()? — Talljoe
I use $.ajax() in jQuery because it gives more options. Then you can just have a listener for success, completed, and error and see what your problem is. — beatgammit
I am using jQuery. Actually, I could have just used xmlhttp.responseText instead of xmlhttp.responseXML. Is $.get() asynchronous? — xsznix
xmlhttp.responseText should always return the contents of the response, while xmlhttp.responseXML will only return if the response is xml. Try logging responseText to see with the response actually is; it could be that its not xml. — monsur

Jollymorphic Jollymorphic · Accepted Answer · 2011-04-02T17:25:00

If you are using Internet Explorer, at least, then you may have a null response because the ContentType header in the response is missing or incorrect. Quoting Microsoft's documentation on the responseXML property:

If the ... Multipurpose Internet Mail Extension (MIME) type was not correctly set to one of the supported MIME types ... then responseXML will be empty.

The supported MIME types for MSXML 6.0 are: "text/xml", "application/xml" or anything that ends with "+xml", for example "application/rss+xml".

The supported MIME types for versions prior to MSXML 6.0 are: "text/xml", "application/xml".

XMLHttpRequest to string

1 Answers