JVM just irks me the wrong way. Probably less than electron / nodejs does but if I'm stuck with one set of primitives and externs (npm) I'd rather use the same one both places even if the JS one is suboptimal in all cases (I've written enough JS that I'll be able to deal.)

Re The shared code thing between server and client for JS I never understood the proposition. You're solving different problems sharing code _never_ made sense.

I think what people were really talking about when they said they wanted it was sharing data. Sharing their object relations, or sharing their mapping code. Or better yet, not having to share mapping because with the same language in both places you no longer need to map data.

And nodejs/browser js does in fact get you all of that. Provided you have clean models and clear conventions / functions to manage that shared state.

Where the story breaks down is the lack of native immutability, and the problems that leads to elsewhere, namely, if you have some data in the client that maps perfectly to serverside data you likely still end up with that serverside version of it including g server side only infoyou don't want exposed. Likely this is the what you should do boundary wise but it is what often ends up happening anyway.

Closure forcing immutability also forces not only the data structures but also the library code that makes reasoning about, and slicing and dicing those structures far easier / natural or I guess you would say isocratic.