How is that really different toolchain-wise from having to compile source code in a language such as Java?
it's not an apt comparison. You can directly write javascript and run it in your browser or in node (or test it out interactively in the node REPL).
I like to play with modules in node interactively (when relevant) because its easier to see what's going on and much easier to iterate (esp. in conjunction with the .load REPL command)