[_pmf_]

> If you just want to program a Synchronous server in the JVM,just stick to Java.

And if you want to program an asynchronous server on the JVM in Java, all of the major and minor servers also support an asynchronous model (you merely lose the ability to program against the Servlet API, which pre-3 was bound to threads).

There's no reason at all to bring JS in for asynchronous behavior.

[sourcesmith]

There is also Vert.x which runs on the JVM but is event driven and asynchronous (as well as providing a reactive API) and supports JavaScript (http://vertx.io/docs/vertx-core/js/) as one of its languages.