JavaScript has come a long way. Due to the widespread use of the web platform, it has become arguably the most popular programming language today. Systems like emscripten have made it possible to compile code written in other languages into JavaScript, so that it can run in the browser.
Writing a JVM in JavaScript is a really bold move. DoppioJVM is a Java Virtual Machine written in 100% pure JavaScript. It is a research project from the PLASMA lab at the University of Massachusetts Amherst, and it is already being used in an educational website that teaches Java programming.