Is there any resource that teaches mixed ES5/ES6 for beginners?

Either I find some ES5 resources, and I have the feeling to spend my time learning stuff I'll never use by myself. Either I find some ES6 resources that need ES5 knowledge as prior requirements.

For example, even some may say I should, I don't wan't to be teached that before, we used "var", and now we use "let". I just want to learn the "let" version.