Detect IE version (prior to v9) in JavaScript

Question

I want to bounce users of our web site to an error page if they\'re using a version of Internet Explorer prior to v9. It\'s just not worth our time and money to

Answer 1

This approach to detecting IE combines the strengths and avoids the weaknesses of jKey's answer using conditional comments and Owen's answer using user agents.

• jKey's approach works up to version 9 and immune to user agent spoofing in IE 8 & 9.

• Owen's approach can fail on IE 5 & 6 (reporting 7) and is susceptible to UA spoofing, but it can detect IE versions >= 10 (now also including 12, which postdates Owen's answer).

  // ----------------------------------------------------------
  // A short snippet for detecting versions of IE
  // ----------------------------------------------------------
  // If you're not in IE (or IE version is less than 5) then:
  //     ie === undefined
  // Thus, to detect IE:
  //     if (ie) {}
  // And to detect the version:
  //     ie === 6 // IE6
  //     ie > 7 // IE8, IE9 ...
  // ----------------------------------------------------------
  var ie = (function(){
      var v = 3,
          div = document.createElement('div'),
          all = div.getElementsByTagName('i');
  
      while (
          div.innerHTML = '',
          all[0]
      );
      if (v <= 4) { // Check for IE>9 using user agent
          var match = navigator.userAgent.match(/(?:MSIE |Trident\/.*; rv:|Edge\/)(\d+)/);
          v = match ? parseInt(match[1]) : undefined;
      }
      return v;
  }());
  

This can be used to set useful classes to your document containing the IE version:

    if (ie) {
        document.documentElement.className += ' ie' + ie;
        if (ie < 9)
            document.documentElement.className += ' ieLT9';
    }

Note that it detects the compatibility mode being used, if IE is in compatability mode. Also note that IE version is mostly useful for older versions (<10); higher versions are more standards-compliant and it's probably better to instead check for features using something like modernizr.js.