[thelist] Browser Detect with JavaScript

[Michael Collins]

OK, I am sure many of you have your own way and reasons for detecting 
browser type and version using JavaScript. There are plenty of 
references for existing scripts that are available but none do 
exactly what I want so I ma making my own. I wanted to share this 
script and ask if anyone sees an improvement on the way I am trying 
to pull this off.

My concept is to use this browser detection only to warn people who 
have a browser less than what I consider standard but not prevent 
them from trying anyhow. Bascially if I detect something that is not 
at least of a certain version than I tell them to download a new 
version. I am targeting browsers that will allow decent support of 
CSS, support for JavaScript 1.2 (though I know IE has its own 
quirkiness in its use of JScript), and in general HTML 4.0.

What I considered approved browsers for these purposes are for Mac 
and Windows Netscape 4.7+ and 4.08 (is allowed since this is 
navigator) and Netscape 6+. IE should be at least 5 on a Mac and 4.5 
on Windows. And for Opera I understand that life began at 3.6. Do you 
concur?

I think though that for CSS I have to extend the minor restriction 
for Netscape to 4.72 is that the case? For Mac and Windows? I am not 
as familiar with Netscape's history on Windows, is Netscape 4.08 for 
Windows the "Navigator" version and equivalent to 4.72 (as is the 
case on the Mac)?

Here is my script in case anyone is interested:

function brwcheck() {
   var agt=navigator.userAgent.toLowerCase();

   var is_win=((agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1));
   var is_mac=(agt.indexOf("mac")!=-1);

   var is_op=(agt.indexOf("opera") !=-1);
   var is_ie=(is_op==false && agt.indexOf("msie") !=-1);
   var is_nav=(is_op==false && ((agt.indexOf("mozilla")!=-1) && 
(agt.indexOf("spoofer")==-1) && (agt.indexOf("compatible")==-1)));

   if (is_op==true) {  var 
is_minor=parseFloat(agt.substring(agt.indexOf('opera')+5,(agt.length-1)));}
   else {
     if(is_ie==true) { var 
is_minor=parseFloat(agt.substring(agt.indexOf('msie')+4,(agt.indexOf('msie')+11)));}
     else{var is_minor=parseFloat(navigator.appVersion);}
   }
   var is_major=parseInt(is_minor);

   var resultck=false;
   if (is_mac) {if (((is_nav==true) && (is_minor >=4.7)) || 
((is_nav==true) && (is_minor==4.08)) || ((is_ie==true) && 
(is_major >=5))) {resultck=true;}}
   else {if        (((is_nav==true) && (is_minor >=4.7)) || 
((is_nav==true) && (is_minor==4.08)) || ((is_ie==true) && 
(is_minor >=4.5)) || ((is_op==true) && (is_minor >=3.6))) 
{resultck=true;}}
   if(resultck==false){
     document.write('<P>&nbsp;<br><font size="4" 
face="Verdana,Arial,Helvetica,sans-serif" 
color="#CC0000"><b><br>Please check that you are using a supported 
Web browser!\r</b></font><font size="3" 
face="Verdana,Arial,Helvetica,sans-serif" color="#CC0000"><br>This 
includes:\r<br>Macintosh: IE 5.0+, Netscape 4.7+ and 6+<br>Windows: 
IE 4.5+, Netscape 4.7+ and 6+\r<p>You can download the latest 
versions for free at the following locations:\r<br><a 
href="http://home.netscape.com/download/">Netscape</a>\r<br><a 
href="http://www.microsoft.com/windows/ie/download/ie55.htm">Internet 
Explorer Windows 5.5</a>\r<br><a 
href="http://www.microsoft.com/mac/products/ie/">Internet Explorer 
Mac 5</a>\r<br><a 
href="http://www.opera.com/download/index.html">Opera</a></font><P>');
   }
}

Michael
-- 
==> Michael Collins
--> Kuwago Web Services
--> Seattle, WA, USA
--> mcollins at nwlink.com
==> www.lassodev.com