I could have used this long time ago but better late than never. It turns out that you can debug javascript after all in VS.Net...very cool.
“Just write the magic "debugger;" line in your javascript code and VS.NET will popup in debug mode (make sure you have unchecked the "Disable script debugging" options in IE -> Tools -> Options -> Advanced). From this point on you can take advantage of step over (F10), step into (F11) and the powerful Watch window displaying all the properties/method of the object you inspect.“
full post...
http://blogs.telerik.com/blogs/rumen_stankov/archive/2006/02/21/125.aspx