I would like to have a very simple client in nodejs (an example) that can receive messages from my contacts in telegram. I just searched in internet but I only get bot samples.
If you want to interact with Telegram data outside one of the official applications (website, mobile or desktop app etc...) you will have to create an App, so you will be required to generate API key and/or use any already existing App which fit your requirement (bots in your case).
Let me underline that with API system it appear difficult to get access to something which is restricted, if you don't have previously grant or add privileges to access it ... Nobody want that anyone could access any data...
Regards