[cutler]

Replacement for a systems language? How are dynamically-typed callbacks, as in Node's fs library, in any way comparable with, say, go routines or good old procedural C++? Async is the worst programming model for building systems.

[z3t4]

The Node.JS libraries also have Sync (not async) alternatives. But everything is async by default. JS/Node is single threaded, but supports multi process concurrency with message passing and sharing of sockets.

I personally prefer callback convention, but it's not the only paradigm. Primises/Futures, and async/await is also very popular.

Node.JS makes you think async, which has a learning curve, but I prefer that over multi threading locks and data races.

Go is also great. But I think JavaScript is much easier.