How to get request digest value from provider hosted app?

Question

I am developing SharePoint 2013 Provider hosted app using javascript REST Api. In order to perform create (POST), or update (MERGE) operations on sharepoint items I need to set

Answer 1

The RequestExecutor actually takes care of the RequestDigest for you. You don't have to get it.

If for some reason, you still want to get the RequestDigest value, try doing the call without changing the context site.