How to get channel updates using Telegram robot?

Question

Node.js

I read that you need to add a bot as an admin to the channel. - added. How do I now look for the latest messages on the channel? and see who entered/left the channel? probably in some way getUpdates. but what to hang it on. that would work from time to time. sorry, I'm stupid a little, I wrote a 1 to 1 bot that communicates. but that the bot would track updates in the group to which he was invited (and he is an admin there) - has not yet been done.