, What Every JavaScript Developer Should Know About ECMAScript 2015 is the book I'd like to read about the new features in the JavaScript language. The book isn't a reference manual or an exhaustive list of everything in the ES2015 specification. Instead, I purposefully selected what I think are the important features we will use in everyday programming.  

1. Improving the development experience when using popular JavaScript libraries
2. Adding support for new JavaScript ECMAScript 2015 (also known as ES2015 and formerly ES6) language and web browser APIs
3. Increasing your productivity in complex JavaScript code bases