JavaScript is arguably one of the most important languages today. The rise of the web has taken JavaScript places it was never conceived to be.
Prior to 2015, the last major update was ECMAScript 5.1, in 2011. However, in the recent years, JavaScript has suddenly seen a huge burst of improvements within a short span of time. In 2015, ECMAScript 2015 (previously called ECMAScript 6) was released and a ton of syntactic constructs were introduced to make writing code less unwieldy.
Till this day, not all browsers have fully implemented the ES2015 specification. Tools such as Babel enable developers to write ES2015 in their apps and Babel transpiles them down to ES5 to be compatible for browsers.
JavaScript is an incredibly versatile language which you can also use to build web servers, native mobile apps and desktop apps.