What is a javascript shell

Does this look desirable to you?

// Replace macros in each .js file
cd('lib');
ls('*.js').forEach(function(file) {
  sed('-i', 'BUILD_VERSION', 'v0.1.2', file);
  sed('-i', /.*REMOVE_THIS_LINE.*
/, '', file);
  sed('-i', /.*REPLACE_LINE_WITH_MACRO.*
/, cat('macro.js'), file);
});
cd('..');

If so, javascript shell could be interesting, it's

a portable (Windows included) implementation of Unix shell commands on top of the Node.js API.

I'm unsure if this could be used as a full-featured login shell, though. (Maybe with some wrapping?)

You could argue that it's not really a shell, but do you know TermKit? It's made of Node.js + Webkit, you could use JS to extend it (I guess); the shell language is still Bash(-ish).