I don't think it is possible right now in VS2010/VS2008 but I'm sure someone must have done or can come up with some workaround using the extensibility of VS2010/VS2008.
Ability to collapse javascript function/comment blocks within script tag in an aspx file editor and in javascript(*.js) file editor the same way we can do in any other editor (c#,vb,xml).
I was just thinking that if it is possible by creating #region
blocks as we do in c# editor.