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You could spend a lot of time figuring out all the pieces of
JavaScript on the client side and Perl on the server side in order to
work out how to use Ajax in your code. However, this is Perl; we like
to be a bit lazy. Thankfully, there's already a module on CPAN to take
the pain out of it: CGI::Ajax (http://search.cpan.org/dist/CGI-Ajax/).
CGI::Ajax provides a small bit of infrastructure for
your CGI programs. You tell it about some of your functions and it sets
up JavaScript to call them and return the results to your page. You
don't need to worry about writing the JavaScript to do this, because CGI::Ajax takes care of it. All you have to do is add some JavaScript calls to the functions defined in your script and let CGI::Ajax deal with the plumbing.
The functions that CGI::Ajax creates in JavaScript for
you all follow more or less the same pattern. They take two parameters:
a list of HTML IDs to get input from, and a second list of HTML IDs to
insert the results into. Having ID attributes in your HTML is a
prerequisite for enabling this behavior. CGI::Ajax handles querying your web page for the input values and inserting the results when the answer comes back from the server.
By making functions in your CGI script available to the browser, you
have the ability to do things that you can't ordinarily do. For
instance, you can look up values in a database, or query the system
load average. Anything you can do in Perl that you couldn't in
JavaScript now becomes possible. Read more... |
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