CODEWITHSUNDEEP
javascriptxmlhttprequest
Amberlamps
Amberlamps

Reputation: 40448

Legacy code to create XMLHttpRequest still valid?

For years I am using the same code snippet to create the XMLHttpRequest object:

var tReq = (function () {
    var tAn;
    if (window.XMLHttpRequest) {
        tAn = new XMLHttpRequest();
    } else if (window.ActiveXObject) try {
        tAn = new ActiveXObject("MSXML2.XMLHTTP");
    } catch (ex) {
        tAn = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return tAn;
}());

I have been using that code for so long that I do not know if it is still up to date.

Does this code still create the XMLHttpRequest in every browser or is there a more efficient solution nowadays (not asking for jQuery)?

Upvotes: 3

Views: 812

Answers (3)

Jared Farrish
Jared Farrish

Reputation: 49188

I remember using this code, some four, five years ago? When the technique first got developed and was still being argued about (anyone remember the don't disable the back button argument?), it was still somewhat patchily supported; this would be around Firefox 1/2. If I recall, this originated as an MS Outlook library that was used to make the Outlook client more responsive, and eventually the technique bled over into browsers.

Having said that, the last two lines are legacy; all modern browsers have and do support the plain XMLHttpRequest, and the last two were only meant for IE anyhow. In the future, this will perhaps be shortened to HTTP or AsyncRequest or whatever, but the fact is, unless you need to support IE6, you really only need the first line.

To wit:

To support versions of Windows Internet Explorer prior to Internet Explorer 7, use the following function to get the XMLHttpRequest object.

function getXMLHttpRequest()  {
    if (window.XMLHttpRequest) {
        return new window.XMLHttpRequest;
    }
    else {
        try {
            return new ActiveXObject("MSXML2.XMLHTTP.3.0");
        }
        catch(ex) {
            return null;
        }
    }
}

http://msdn.microsoft.com/en-us/library/ie/ms535874%28v=vs.85%29.aspx

So, you don't really need it anymore. As Truth says, libraries like jQuery, Angular and their ilk will subsume this into the background over time. But accessing it directly is not a problem either.

Also worth linking to MSDN's About Native XMLHTTP, courtesy of RobW's comment under the question. The gist of this is that Group Policy or individual IE policy may disable native XMLHttpRequest, so it may still be useful to enable ActiveX as a workaround, although (at least at this point) it seems a little crayon tinfoil to disable that while allowing the much more "problematic" ActiveX subsystem. A possible explanation of this is bandwidth, concurrent connections or some other network-level concern. Weird.

Upvotes: 4

David G
David G

Reputation: 96790

Nothings wrong with your approach. This is how I would do it though if it helps.

var tReq = (function(window) {
    var a = window,
        b = a.XMLHttpRequest,
        c = a.ActiveXObject,

        if (!b && c) {
            try {
                return new c("MSXML2.XMLHTTP");
            } catch (e) {
                return new c("Microsoft.XMLHTTP");
            }
        }
        return new b();
})(this);​

Upvotes: 0

Madara's Ghost
Madara's Ghost

Reputation: 174947

Actually (and I can't believe I'm saying this), jQuery may not be such a bad solution.

In fact, jQuery was invented to sort out browser oddities, it's a form of a massive adapter pattern.

In that sense, jQuery's .ajax() method and its aliases are a perfect fit for the job.

As for the solution you currently have, it looks fine to me. Should work for every browser past IE7 (inclusive).

Upvotes: 0

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