Javascript: detection browser type

To detect the browser type in JavaScript: (>-1 shows the bowser type)

           var is_firefox = navigator.userAgent.toLowerCase().indexOf('firefox');
           var is_msie = navigator.userAgent.toLowerCase().indexOf('msie');

           var is_chrome = navigator.userAgent.toLowerCase().indexOf('chrome'); 

           var is_safari = navigator.userAgent.toLowerCase().indexOf('safari'); 

          if(is_firefox>-1)

           {

                     alert("Your browser is FireFox");

           }

          else if(is_msie>-1)

          {

                       alert("Your browser is MSIE");

           }

           else if(is_chrome>-1)

           {

                      alert("Your browser is Chrome");

           }

          elseif(is_safari>-1)

         {

                       alert("Your browser is Safari");

          }

Although Safari is originally from Mac, you can download it for Windows:
http://support.apple.com/downloads/Safari_3_2_2_for_Windows

All these 4 browsers can be tested in Windows.