The people live in a bubble, they don't considerer that there is others kind of software that required more (so much more) business logic, that only an insane man can try to solve with js.
The problems that can be solved using js grow large with each passing year though. I wrote a video recording and exporting app for a client this year using web technolgies (html + js + node). I couldn't have imagined that being possible 10 years ago.
I am not talking about this. What I means it's when you have to deal with more complex interaction, between different systems, old technologies, ...
What you say it's true, JS it's going to evolve in the next years until to convert in something totally different, you will see. Some people call that reinvent the wheel.
I am not against JS at all, I just dont think every single problem can be resolve with that, sorry.
In this case, it captures and streams from the computer it is running on via a video capture card. The application is for archiving audio and video from an external box that it monitors.
The nice thing about doing it that way, is that adding the capability to stream real-time from the external box that is being monitored is as easy as opening the ports to external access.
Looking at MVC, a common recommendation is to put the business logic into the model. "Fat models, skinny controllers"
IMHO the JS frontend should contain almost no business logic. Rather it should be handled either by "the" backend or if it is really that complex, by a separate web service. (Self-speaking that this service can be written in any language that makes sense.)
(On the other hand, the success of node.js proves that medium sized applications can be written in pure JS.)