How Can I Add Properties To An Object In Ie6?

I've got a particularly tricky problem using AJAX, which works fine in IE7 and Firefox, but not in IE6. I have a very simple home-grown AJAX framework, which requires that I extend

Solution 1:

On IE7 you are getting a ‘native JavaScript’ XMLHttpRequest object. As with all JavaScript objects you can add arbitrary properties to them without problem — although it's not always a good idea, because if a future browser added a real ‘onReturnFunc’ member of its own you'd then confuse it.

On IE6, or IE7 when the ‘native XMLHttpRequest’ option is disabled, you fall back to using the original ActiveX XMLHttpRequest. However, ActiveX objects have quite different behaviour to JavaScript objects and one of the differences is you can't add arbitrary properties.

Generally, you should have your own wrapper class that holds any extra data you need, and which holds a reference to the ‘real’ XMLHttpRequest object.

Solution 2:

The problem is that its the browser provided XMLHttpRequest that supports expandos. However IE6 does not have a XMLHttpRequest so your code drops to using the ActiveXObject. MSXML provided object does not support expandos.

A better approach would be to use a closure anyway, something like:-

functiongetContentForElem(url, elem, completed)
{
    var xhr = getXhr()
    xhr.open("GET", url, true)
    xhr.onreadystatechange = fnstatechange
    xhr.send()
    return xhr;

    functionfnstatechange()
    {
       if (xhr.readyState == 4)
       {
           if (xhr.status == 200)
           {
                elem.innerHTML = xhr.responseText;
           }
           if (completed) completed(xhr)
       }
    }
}

functiongetXhr()
{
    var xhr;
    if (window.XMLHttpRequest)
        xhr = newXMLHttpRequest();
    else
        xhr = newActiveXObject("MSXML2.XMLHTTP.3.0");
    return xhr;
}