Learning the Basics
About the Language
As a C# developer, I struggled with these parts more than others.
The this keyword. Pay particular attention to how, unlike in C#, the context of this changes depending on invocation. It is different than your intuition would have it be.
0 === ""does not. In neither case will you get a type error!
The role of call, apply, and the ‘array like’ arguments keywords. If you delve into the source of libraries, you are going to encounter these as they add a lot of power to the language.