AvatarJS
From APIDesign
AvatarJS was an attempt to re-implement NodeJS on top of the JVM. These days just download GraalVM and you'll get JavaScript and Java for free. Compatibility is guaranteed.
Tooling
The NetBeans tooling (including excellent debugging, see Nashorn).
Speed
[[GraalVM] includes as fast as V8 implementation of JavaScript. Predicted presentation about next generation Nashorn many years ago...