How to get list of folders in sidebar? How to get the list of folders in the sidebar using AppleScript?

It is okay to get the list of all items too since I will be able to search for them
You can't.  Finder's Sidebar is a location for shortcuts to be easily accessible by the user.

From Apple's Human Interface Design Guidelines:  


  the sidebar in a Finder window includes a list of frequently accessed locations and tag-based search shortcuts. The user can select one to access its contents or results in the main portion of the window.


Additionally, having a folder list is not practical in this element. Anything more than 2 levels of hierarchy (which is highly plausible in a folder listing) is discouraged.  In this instance, Apple states that a column view be used.


  In general, refrain from exposing more than two levels of hierarchy within a sidebar. In some cases, a second sidebar may be warranted
  when a data hierarchy is deeper than two levels. If your app requires
  the navigation of deeply nested objects, consider implementing a
  column view.


Bottom line; Apple discourages 3rd party developers from doing this, meaning Apple's Finder is definitely not going to show files like this.  

You can put a shortcut to a folder, but you won't get a list of folders.