@bbsmooth But what do I do if there is a very good introductory book but published in 2014 so not ES6?
Personally, I would not waste my money on a book that old when there are so many more recent introductory JS books. But I don’t know what book you are referring to or why you think it is so good. You may have a good reason for wanting it that outweighs the negatives. But if you are serious about JS then you will have to buy a more up to date book at some point so why not start now?
What up to date book for absolute beginner who only knows HTML/CSS would you recommend to learn JavaScript? And no, Eloquent is not for beginners. Please suggest oher 2-3 @bbsmooth
I gave you one suggestion above. I don’t have any others. I don’t read many books for beginners any more since I’ve been doing this for a long time 
At some point you’ll just need to buy one and get learning.
Good luck.
and for your questions:
yes, you can learn the basics from one book written in es5 standard.
You will then have to do the switch from the few outdated things in the es5 standard, to those in the es6 that replaced those
like var replaced by let and const
more often than not the features introduced in es6 are complementary to es5, so you could do that. Most stuff didn’t change, there are just new features.
I think you should really go for Eloquent Javascript…helps alot