One thing that gave me a glimpse into the big picture of JavaScript was the MDN docs. You can navigate to the built in objects, then have a look at the most commonly used ones like Array, String, Object. Look at the method signatures and try to implement an example of the ones that you think you can handle. Good workout, and reference material.

This is wonderful. I often know there is a way to do what I need, but can't remember enough to search online for it. This is very concise and will help with that.

This looks very useful! The one thing I don't like is specifically labelling things as "ES6" features. ES6 is 4 years old now, and there's a new release every year. We're up to ES10/ES2019 now, and in general people should be using it. (Possibly with a compiler if they still need to support older interpreters.) There is nothing special about ES5 that's now a decade or of date.

http://devdocs.io/javascript/