[checker]

Sounds like parent was using async to mean that JS has single-threaded concurrent functions by default.

Disclaimer: I'm just the messenger here so you might hate what follows, the community is choosing the words.

Concurrency as a keyword is increasingly being used to differentiate single-threaded event handling from parallel processing (threads). As long as event handling is quick enough, it can give the illusion of parallel processing. And in some cases it can outperform parallel processing because the cost of context switching between events can be lower than context switching between threads. See https://medium.com/@caophuc799/nginx-architecture-and-why-ca...

The async keyword, in practice, simplifies the callback boilerplate required to handle the event model. When used in communication, async is increasingly being used as a word to describe "Single-threaded Concurrent Functions Built On Hidden Event Handling", because there is no succinct way of saying STCFBOHEH in English.

So: JS has async/STCFBOHEH/context-switching on its functions by default whereas Java's functions are (by default) executed in order without async/STCFBOHEH/context-switching.

[recursive]

I'm not an expert or anything, but I've never seen an implementation of event handling that was anything other than STCFBOHEH. (hadn't heard the term)

My understanding of "async" as a language feature is basically support for an `await` keyword. Having a message loop and event dispatcher seems like a less useful definition, but good to know, I guess.