Javascript is also a dynamically typed script language, which Google managed to make at least one order of magnitude faster with V8. It's likely same tricks can be applied to Ruby.
And language benchmarks don't tell the whole story. In Java, idiomatic and typical code will be optimized very well whereas in Javascript such code runs easily at least an order of magnitude slower than its potential. Try to run some idiomatic JS through https://github.com/petkaantonov/nodeperf/ and see it explode :)
So even if Javascript can be shown in some benchmark to close on the JVM, the benchmarks are ignoring the fact that you cannot write Javascript carelessly to get anywhere near those speeds unlike with Java.
Seems that node.js outperforms the JVM for WebDev nowadays.