For a project I\'m tangentially working on, I need a way to compile JavaScript into some intermediate language or bytecode so that I can single-step through it. I know that
Not exactly sure of your needs, however maybe Rhino could work for you.
The JavaScript compiler translates JavaScript source into Java class files. The resulting Java class files can then be loaded and executed at another time, providing a convenient method for transfering JavaScript, and for avoiding translation cost.
More about the compile function is located here.