Tiny Javascript to detect versions of Internet Explorer

Written November 23. 2006, at 00:06 GMT.

Here's a nifty little piece of Javascript code that reliably detects the presence of Microsoft's Internet Explorer browser with absolutely minimal processing overhead for all other browsers:

var is_ie/*@cc_on = {
  // quirksmode : (document.compatMode=="BackCompat"),
  version : parseFloat(navigator.appVersion.match(/MSIE (.+?);/)[1])

(Uncomment the second line if you also wish to check whether IE is running in "compatibility" (quirks) mode or in standards-mode.)

The check relies on Microsoft's proprietary conditional compilation syntax, to make sure the object assignment and version number parsing is only performed by Microsoft's browsers.

All other browsers cheerfully ignore the Javascript comment block (/* ... */) so what they end up with is essentially this:

var is_ie;

...which evaluates as an implicit false, when used as a condition. This allows us to set up conditions like this one:

if (is_ie && (is_ie.version < 7))
  // do IE specific stuff
  // default behavior for other browsers

I lifted the basic idea from Javascript God, Dean Edwards, and extended it to include the version number - which is tremendously useful when dealing with IE's quirky behavior.

More like this: English Entries, HTML/CSS, Javascript.

Reader Comments (6)

  1. Sindri replies:

    if ( is_ie ) { document.location.href = "http://www.mozilla.com/en-US/firefox/"; }


    November 23. 2006 kl. 12:19 GMT | #

  2. Kiddi Geir replies:

    hehe góđur : )

    November 24. 2006 kl. 12:40 GMT | #

  3. Már Örlygsson: Minor Javascript updates

    "Tonight I updated the code provided in a couple of recent posts: Added an optional feature to the tiny IE browser detection script Posted a significant update to my unobtrusive script workaround for IE's "Click to activate" feature, that makes..." Read more

    December 13. 2006 kl. 23:46 GMT | #

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