Detect ClickOnce support

README

This detects the presence of ClickOnce in IE, Chrome (with extension), and 
Firefox (with extension). 

It doesn't work if Firefox is using Microsoft's .NET Framework Assistant when 
adding .NET information to the User Agent string is turned off (the default 
setting as of late). I personally worked around this by using server logic to 
detect if the X-ClickOnceSupport header was set.

clickonce.js

(function () {

   // Detect if ClickOnce is supported by the browser. 
   // Roughly based on http://stackoverflow.com/a/4653175/117402

   var hasMimeSupport = function (desiredMime) {
      var mimes = window.navigator.mimeTypes,
          hasSupport = false;

      for (var i = 0; i < mimes.length; i++) {
         var mime = mimes[i];

         if (mime.type == desiredMime) {
            hasSupport = true;
         }
      }

      return hasSupport;
   };

   var sniffForClickOnce = function () {
      var userAgent = window.navigator.userAgent.toUpperCase(),
          hasNativeDotNet = userAgent.indexOf('.NET CLR 3.5') >= 0;

      return hasNativeDotNet || hasMimeSupport("application/x-ms-application");
   };

   window.clickOnce = sniffForClickOnce();

})();