This work-around copies the values (in your examples), or the references (if the props are functions or objects), which is just wasted cycles and memory bloat.

This work-around copies the values (in your examples), or the references (if the props are functions or objects), which is just wasted cycles and memory bloat. It's harder for runtimes to optimize, because with that mixin `o1` changes its shape. It's harders for IDEs to infer the type of `o1`, which will hurt navigating and searching through your codebase with confidence. Implementing OOP in JS with hacks like this is worse, in pretty much all ways, apart from the intellectual kick many devs get of avoiding OOP at all cost, as opposed to just using built-in language features.