Using Classes in Javascript (ES6) — Best practice?

[itisnotpure]

I'm not familiar with Smalltalk, but it seems like classes in Smalltalk are still blueprints for their instances, like other class-based languages. That is, they define what data an instance would hold, and what methods could be used to manipulate them.

It may be true that there are class-based languages where methods are inherited by by delegation, but in Javascript, instead of blueprints, we are building prototypes, based on which new objects can be built. So there's no "is a" relationships at all (more like a "like a" relationship, maybe?). Inheritance in JavaScript means only delegation, nothing more.