MediaWiki: how to extract the wiki text (only) from an article?

• https://stackoverflow.com/questions/1625162/get-text-content-from-mediawiki-page-via-api
• https://stackoverflow.com/questions/33844207/how-to-get-wikipedia-content-as-text-by-api
• https://www.mediawiki.org/w/api.php?action=help&modules=query

The above articles (Stack Overflow) do not exactly answer my question, but they are rather close.

The key is using api.php and action=query.

Purpose: I want to compare articles of two rather close wikis, and the articles have a common ancestor.