I looked at this a long time ago when i experimented with templating (the branch may still be in SVN). You will need to duplicate the validation in both the front and back end for a few reasons:

1) you can't guarantee that the client supports javascript (unless we make this mandatory)
2) the back end needs validation to prevent errors cropping up is someone bypasses the front end validation.

   ... Glenn
Glenn Henshaw                     Logical Outcome Ltd.         
e: thraxisp@logicaloutcome.ca     w: www.logicaloutcome.ca

On Feb 26, 2014, at 4:35 AM, Cyril CHARLIER <cyril.charlier+mantbtdev@gmail.com> wrote:

> controle the mail [ddd@xxx.xxx]

Need to be careful about duplicating logic here, and potentially ending
up with inconsistent validation of email addresses.

Refer to email_is_valid() function in email_api.php

thanks, i will look at it to be logic in the control. 
for me, the logic can be duplicated
the user can be informed in JS/CSS that a field is required : a user logic (more user-friendly)
the program (mantis) must controled the field required : a security logic

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