Can't create a date picker with an XWiki.JavaScriptExtension object

This is the xar with the reproduced bug.

Hi Guillaume, three remarks:

1. You should execute the JavaScript code after the page is loaded. The best practice is to write something like this:

   (function() {
     function init() {
       // This should be the entry point for your JavaScript code.
       // ...
       return true;
     }
     (XWiki.domIsLoaded && init()) || document.observe('xwiki:dom:loaded', init);
   })();
   

   If you're defining new widgets, then it's recommended to use the XWiki namespace like this:

   var XWiki = (function (XWiki) {
     // Start XWiki augmentation.
     XWiki.MyNewWidget = Class.create({
       ...
     })
   
     function init() {
       // Enhance the current page with your new widget.
       // ...
       return true;
     }
   
     (XWiki.domIsLoaded && init()) || document.observe('xwiki:dom:loaded', init);
   
     // End XWiki augmentation.
     return XWiki;
   }(XWiki || {}));
   

2. Since the date picker application is not maintained by the XWiki development team you shouldn't report its issues in XWiki Platform but in http://jira.xwiki.org/browse/XCONTRIB/component/10910 instead.
3. If you're using a newer version of XWiki Enterprise, there is a date picker available by default, used by the AppWithinMinutes:

   {{velocity}}
   {{html}}
   #set($discard = $xwiki.ssx.use("AppWithinMinutes.Date"))
   #set($discard = $xwiki.jsx.use("AppWithinMinutes.Date"))
   <input type="text" class="datetime" title="dd/mm/yyyy" />
   {{/html}}
   {{/velocity}}
   

   (function() {
   function init() {
     // This is required only in view mode. In edit mode it is done automatically by AppWithinMinutes.Date JSX.
     $$('input.datetime').each(function(dateTimeInput) {
       new XWiki.DateTimePicker(dateTimeInput, dateTimeInput.title);
     });
     return true;
   }
   
   (XWiki.domIsLoaded && init()) || document.observe('xwiki:dom:loaded', init);
   })();
   

Guillaume, since you didn't reply to my comment I'll assume my suggestion helped you fix the problem so I'm going to close this issue. Please reopen if you still have problems.

Note that I'm planning to fix XWIKI-1448 in 4.3M2 so we're going to have a default date picker for all date fields.