Retrive all items including sub folder items in CAML [duplicate]

This question already has an answer here:

• CAML Query for sub folder documents javascript 2 answers

I am trying to retrieve all files and sub folders of a specific folder in Document Library.

The structure looks like

/sitename/shared documents/folder1/
/sitename/shared documents/folder123/
/sitename/shared documents/folder123456/

I want to get all items including sub folder items under folder1 by using CAML, JSOM.