Nowadays, browser vendors are releasing new features in short iterations, and users receive updates quite often. This helps developers take advantage of bleeding-edge web technologies. ES2015 is already standardized. The implementation of the latest version of the language has already started in the major browsers. Learning the new syntax and taking advantage of it will not only increase our productivity as developers but will also prepare us for the near future when all browsers will have full support for it. This makes it essential to start using the latest syntax now.
The requirements of some projects may enforce us to support older browsers, which do not support any ES2015 features. In this case, we can directly write ECMAScript 5, which has a different syntax, but has semantics equivalent to ES2015. On the other hand, a better approach will be...