In the tutorial they are most likely using the latest version of Node JS, which allows you to write ES6 (without ES6 modules). There's no need to configure anything for that.
If you have the same question about javascript that needs to be executed in the browser, then you'll need a build tool that transpiles ES6 to ES5. There are many tutorials out there that explain you how to do this. An example would be the following link: ccoenraets.github.io/es6-tutorial/setup-babel.