(1) Modern JS libraries and frameworks such as React, Angular or Vue which are basic tools that make writing modern, large scale web apps a lot easier and faster. However, all these libraries are still 100% based on JS. This means that you should become really good at JS before learning and using any of these frameworks, and not just jump into your first framework after you know how to write, for example, 10 lines of JS. 

(2) Your library of choice might not always be as popular as it is today. And the best way to be prepared is becoming really good at JS. Because, then, you can easily learn whatever is popular next. No matter what anyone tells you, learning JS properly is the single best investment to be good at web development. 

(3) JS language and the web browser are actually two separate things. What that means is that JS can also run outside of web browsers. For example, it’s possible to use JS on a web server using a very popular technology called Node.js which doesn’t need any browser at all. And this allows us to create backend apps, which are simply apps that run on a web server and interact with databases and the like. 

(4) On the other hand, we are creating front end apps when we use JS in the browser.

(5) We can actually also use JS to build native mobile applications and native desktop applications for any phone and computer operating system.  Modern tools, like React Native, Ionic Framework and tools like Electron have completely changed the whole development industry in recent years, making things previously impossible possible.

(6) There was a huge update to the language in 2015, which is officially called ES2015. But most people call it ES6 simply because it was released after ES5. 

(7) ES stands for ECMAscript. After ES2015, there is now a yearly new release with a couple of new JS features. In all of these releases or versions, starting from ES2015, is what we call modern JS. 

(8) However, you need to understand what came before ES2015: ES5.