How to change the number of posts that WordPress JSON API loads per page.
The default is 25, because of low internet connection I want to make it less.
As explained in the documentation, you can specify the maximum number of posts in the response with the count parameter in your request.
Example with user-friendly permalinks configured:
http://www.example.org/api/get_posts/?count=10
if you are on newer WordPress version then acording to their docs
https://developer.wordpress.org/rest-api/reference/posts/#arguments
per_page argument is used now.. like
https://www.example.org/api/get_posts/?per_page=100