Reliable Javascript Version Detection?

I have been struggling around with trying to figure out a reliable manner for detecting the Javascript version a given browser is using.

Basically, there are two half-decent ways that I have found, neither one being foolproof.

One way is using javascript tags with the language attribute, as in the following code:


Code:
<SCRIPT LANGUAGE="Javascript"><!--
gVersion="1.0";
//-->
</SCRIPT>
<SCRIPT LANGUAGE="Javascript1.1"><!--
gVersion="1.1";
//-->
</SCRIPT>
<SCRIPT LANGUAGE="Javascript1.2"><!--
gVersion="1.2";
//-->
</SCRIPT>
<SCRIPT LANGUAGE="Javascript1.3"><!--
gVersion="1.3";
//-->
</SCRIPT>
<SCRIPT LANGUAGE="Javascript1.4"><!--
gVersion="1.4";
//-->
</SCRIPT>
<SCRIPT LANGUAGE="Javascript1.5"><!--
gVersion="1.5";
//-->
</SCRIPT>


This works fine but it is not very elegant. Another disadvantage is that it is not XHTML compliant.

The other way is using some sniffer scripting like that found in the JavaScript Browser Sniffer (Web Reference).

However, this is not very reliable as it needs to be constantly updated to take newer browsers into consideration. Also, on my system it gave an incorrect Javasctipt version of 1.3 when it should have given 1.5 (according to the first option above).

I was just wondering if there was a more dependable way of doing this.

Maybe it would just be better to avoid unnecessary headaches and restrict myself to W3C compliant brwosers.