This week version 2.0 of the V8 package has been released to CRAN. Go get it now!
install.packages("V8")
The V8 package provides an embedded JavaScript engine that can be used inside of R. You can use it interactively as a JavaScript console, but it is mostly useful for wrapping JavaScript libraries in R packages. Some cool examples include jsonld, jsonvalidate, and daff.
This major and much anticipated upgrade brings a new version of the JavaScript engine, effectively upgrading the JavaScript language. This opens up a lot of new possibilities, but it can also introduce some subtle behavioral changes, so read on carefully.