Check out my book (free online): “Exploring ES2016 and ES2017”.
Update 2017-01-29: At the TC39 meeting in January 2017, the last feature of ECMAScript 2017, “Shared memory and atomics” advanced to stage 4. That means that its feature set is now complete, as listed below.
Major new features:
Minor new features:
Object.getOwnPropertyDescriptors()(Jordan Harband, Andrea Giammarchi)
They refer to maturity stages in the so-called “TC39 process”. Check chapter “The TC39 process for ECMAScript features” in “Exploring ES2016 and ES2017” for more information.
If you are wondering what stages various proposed features are in, consult the readme of the ECMA-262 GitHub repository.
The following books by me are free to read online: