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Reliable IE 7 detection with JavaScript?

Currently, the most accurate method of detecting Internet Explorer 7 with JavaScript is the following:

var ie7 = (document.all && !window.opera && window.XMLHttpRequest) ? true : false;

There’s an alternate, but in my opinion less future proof, method:

var ie7 = (typeof document.addEventListener != 'function' && window.XMLHttpRequest) ? true : false;

I don’t believe they will ever drop document.all, but I’m certain they are going to fix addEventListener method.

Test conditions

Here’s a quick breakdown of objects/methods tested:

document.all
returns true in all Internet Explorer versions and also in Opera
window.opera
also known as opera object, returns true in Opera
window.XMLHttpRequest
returns true in Firefox, Opera, Safari and IE 7
returns false in IE 6 and lower

So far, I haven’t found flaws in this detection method. However, if someone knows better, please do tell. Ken Snyder pointed out that the native XMLHttpRequest can be disabled in IE 7 by unchecking Tools -> Options -> Advanced -> “Enable native XMLHTTP support” option… Bummer!

Conditional Comments

Last, but not least, you can always set ie7 variable to true inside conditional comments:

<!––[if IE 7]>
<script type="text/javascript">ie7 = true;</script>
<![endif]––>

Time designation No. 2006.10.31.19:15
Cat: coding/design.

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8 shouts to “Reliable IE 7 detection with JavaScript?”

  1. Nick Fitzsimons
    001—2006.10.31.21:07

    You don’t need to use the triadic operator, as your bracketed condition returns a Boolean value. Just use

    var ie7 = (document.all && !window.opera && window.XMLHttpRequest);

    (although the Conditional Comment method is rather elegant, IMHO.)

  2. Aleksandar
    002—2006.10.31.21:56

    Wow, great tip about window.XMLHttpRequest, which I might find a use for, very soon.

  3. Berislav Lopac
    003—2006.11.01.00:09

    The best approach is not to test for browsers in general, but to test for only those features you need. If you need document.all, test for it, not for a particular version of IE.

  4. marko
    004—2006.11.01.16:56

    Berislav, sometimes you simply can’t test for a method or object property.

    Testing typeof document.style.minHeight returns string in all IE versions, but in IE 6 and lower, you can’t actually apply it, due to unsupported CSS property min-height.

    What’s even worse, some other element.style object properties, that have unsupported CSS counterparts in IE 6 or lower (for example document.style.maxHeight) return expectable undefined, so there’s no key one could rely on.

    Or maybe I’m missing something here…

  5. marko
    005—2006.11.01.17:02

    Nick, true that… thanks!

  6. DannyB
    006—2006.11.15.21:12

    You could use conditional compilation… untested but should work…
    isIE7 = false;
    /*@cc_on
      @if (@_jscript_version == 7)
        isIE7 = true;
      @end
    @*/

  7. ken snyder
    007—2006.11.18.01:41

    Unfortunately, IE7 has an option to disable native support for XMLHTTP. Unchecking Tools > Options > Advanced > “Enable native XMLHTTP support” causes window.XMLHttpRequest to be undefined. Tested using following block:

    <script>
    document.write(window.XMLHttpRequest);
    </script>

  8. And Clover
    008—2006.11.21.14:19

    @if (@_jscript_version == 7)

    Incidentally the correct _jscript_version value for IE7 is 5.7. (Similarly, IE6 is 5.6.)

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