Ajax, JSON

AJAX - https://learn.javascript.ru/ajax
https://habr.com/ru/post/14246/
https://www.youtube.com/watch?v=lEfp6_ByY-Q

JSON - https://learn.javascript.ru/json

https://developer.mozilla.org/ru/docs/Learn/JavaScript/%D0%9E%D0%B1%D1%8A%D0%B5%D0%BA%D1%82%D1%8B/JSON