Checking browser version & JavaScript enabled

[Krish Pat]

Greetings to everyone,
How do I check for the browser version(IE or Netscape) on the client machine and also check if JavaScript is enabled using JavaScript? If JavaScript is disabled or an older version of a browser is used, I don't want to allow the client to enter into my application which is in Java/JSP.
Thanks a gazillion in advance,

[Bear Bibeault]

You can grab the "user-agent" request header in order to sniff the browser and version. But keep in mind that this is not fool-proof since the header can be spoofed. Also parsing this header is not deterministic since there is no "standard" format for what is returned.
If you are just checking for a few major browsers, then you can check the headers they return and code some specific checks. But a general solution is difficult. (For example, if someone using a 3Com Audrey hits your page, it will report that it is Netscape 4 running on Windows 98!)
You can't check if JavaScript is enabled using JavaScript because if it isn't enabled, you can't run ANY.
There are some tricks you can use though, that have been discussed in these forums. Do a search and you are liable to find a few.
hth,
bear

[Bear Bibeault]

P.S. Here's a list of some known user-agent strings. Be afraid, be very afraid!
hth,
bear
[ March 04, 2003: Message edited by: Bear Bibeault ]

[sunitha reghu]

Another option is using a <noscript> tag
if the javascript is enabled direct the user to one link if not tell the user to click the link which doesnt use js
<Script language="JavaScript">
document.write(" ");//check for js enabled
</Script>
<NoScript>
JavaScript is disabled. pls use this link (www.watever.com)to access my homepage
</NoScript>

[sampy jagan]

To determine if a user has JavaScript enabled, the <noscript> tag suggested by Sunita seems to be a good option.
Alternatively you can create a HIDDEN form field in the HTML and call a JavaScript function on the onload event, altering the value of this HIDDEN form field. That way, if the form field has been altered, then we know JavaScript is enabled (else the JavaScript function that alters the HIDDEN form field wouldn't have been called).
Here is the sample code for Checking Borwser Name & Ver.

  
<SCRIPT LANGUAGE="JavaScript">
var browsername;
var browserVersion;
// Checks the Browser Name & Version
function checkBrowser() {
  browsername = navigator.appName;
  // Sets the version number (e.g., 4.03)
  browserVersion = parseFloat(navigator.appVersion);
  if(browsername.indexOf("Netscape")!= -1) {
    browsername="NS";
  } else {
    if(browsername.indexOf("Microsoft")!=-1) {
      browsername="MSIE";
    } else {
      browsername="N/A";
      alert("Unknown browser: " + browsername);
    }
  }
  //-- Your code goes here........
  alert("Your Browser Name : " + browsername + " Version : " + browserVersion);
}
</SCRIPT>

call the above functions on the body onload event�
Regards
Jagan

[Krish Pat]

Thank you everyone for the insight on how to approach this. I am going to try out the suggestions right away................
Krish