I considered (and actually started writing) an extra chapter on ES6, but the current state of the standard is poorly documented and still in flux. Also, it's a

I considered (and actually started writing) an extra chapter on ES6, but the current state of the standard is poorly documented and still in flux. Also, it's a huge standard, so it'd have taken two or three chapters at least to cover it properly. For something that won't be supported for a while yet (without using a transpiler), that seemed too much bother. I might add such chapters in the future.