Transpiling Recap
NOTE: As of the creation of this course (circa Winter 2016), most of ES6 is supported by the current set of browsers. But that's "most", not "all", unfortunately. And that's also referring to "current" browsers. There are plenty of older browsers that do not support many, if any, of the new ES6 additions. However, it is safe to say that pretty much every browser supports the previous version of the language (ES5.1).
Transpiling ES6 code to ES5 code.
Transpiling Recap
It's important to stay on top of all the changes JavaScript is going through. The best way to do that is to start making use of the new features that are added. The problem is that not all browsers support these new features. So to have your cake and eat it too, you can write in ES6 and then use a transpiler to convert it to ES5 code. This lets you transform your project's code base to the newest version of the language while still letting it run everywhere. Then, once all of the browsers your app has to run on fully support ES6 code, you can stop transpiling your code and just serve the straight ES6 code, directly!