React Express

ES2015, or ECMAScript 2015, is the first significant update to the language since ES5 was initially released in 2009. You'll often see ES2015 called by its original name, ES6, since it's the 6th version of ECMAScript. Many ES2015 features are already available in modern JavaScript engines. However, for maximum browser compatibility, it's still safest to use Babel and compile down to ES5.
ES2015 Highlights
Let's take a look at some of the new language features we'll be using, and how they get compiled through Babel. There are a lot of language features to go through, so if you get tired, you can move on to the React API, and finish up the language sections another time.