Testing for JavaScript

Category:	CGI Programming
Author/Contact Info	Andrew Kenton Mitchell Andrew@AndrewKMitchell.com http://www.AndrewKMitchell.com
Description:	I had a situation where I needed to know if my visitor's browers supported JavaScript. Here is the code I used.
#!/usr/bin/perl #Hash Array containg list of pages to display depending on test result +s. %resultURLs = ( 'PASS', 'http://www.mscorp.org/cgi-bin/invo.pl', 'FAIL', 'http://www.mscorp.org/js/invorder.pl/nojs.htm +l' ); #URL of this script. $scriptURL = "/cgi-bin/invorder_djs.pl"; #Read hidden form results and decide what to do. require "lib/cgi-lib.pl"; #You can use CGI.pm if you like. &ReadParse; if (!$in{'jstest'}){ &runJSTest; } else{ $result = uc $in{'jstest'}; $url = $resultURLs{$result}; print "Location: $url\n\n"; exit; } #Print HTML output that handles the testing. sub runJSTest{ print <<END_OF_HTML; <html> <head> <title>CHECKING YOUR SYSTEM FOR INSTALLED COMPONENTS...</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1 +"> #Redirect to error page if JavaScript found within 5 seconds. <meta http-equiv="refresh" content="5;URL=$scriptURL?jstest=fail"> </head> <body bgcolor="#FFFFFF" onload="testJS()"> <script language="JavaScript"> <!-- #If JavaScript is enabled this functions is run thereby returning a va +lue of true. function testJS() { document.jstestform.submit(); } //--> </script> <table width="7%" border="0" cellspacing="0" cellpadding="0" align="ce +nter"> <tr> <td nowrap align="center"> <p><b><font face="Arial">PLEASE WAIT<b><img src="/images/pe +riod_ani.gif" width="18" height="12"></b></font></b></p> <p><font face="Arial"><b>CHECKING YOUR SYSTEM FOR + INSTALLED COMPONENTS<img src="/images/period_ani.gif" widt +h="18" height="12"></b></font></p> <p><b><tt><font face="Arial">IF THIS PAGE DOES NO +T CHANGE WITHIN 10 SECONDS, PLEASE <a h +ref="$scriptURL?jstest=fail">CLICK HERE</a>.</font></tt></b></p> </td> </tr> </table> #Hidden form that returns the results, if JavaScript is enabled. <form name="jstestform" method="post" action="$scriptURL"> <input type="hidden" name="jstest" value="pass"> </form> </body> </html> END_OF_HTML exit; } 2001-03-13 Edit by Corion : Fixed formatting 2001-03-13 Edit by akm2 : Enhanced code readibility

Comment on Testing for JavaScript Download Code

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Re: Testing for JavaScript
by arturo (Vicar) on Mar 13, 2001 at 20:42 UTC

A few comments here that might help you improve the code, maintainability-wise.

I'd use CGI for parsing the input, even if you don't like the code generation functions it provides (you appear to be working with some old docs, or is it an old version of Perl?)

# to duplicate cgi-lib.pl and ReadParse (not that you need to -- you c
+ould use more native CGI.pm methods)
use CGI qw(param);
my %in = map {$_ => param($_) } param;
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Instead of that gaggle of print statements, you might check out using "here documents", which work like:

print <<END_OF_HTML;
<html>
 <head>
 <title>Hi!</title>
 </head>
 <body>
 <h1>Javascript is $in{jstest}</h1>
 <p>Isn't that neat?
 </body>
</html>
END_OF_HTML
[download]

I find that sort of thing easier to maintain and less visually messy (no escaping quotes!)

Oh, and I *strongly* recommend use strict (and strict.pm, for that matter). Also, since this is a CGI, you should use the -T switch on your #! line.

I like your use of the JS form submission, that's a good way around the problem with the cookie solution I suggested!

Philosophy can be made out of anything. Or less -- Jerry A. Fodor

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