A project I work on used ShellJS to run a node.js based JS compiler, but it was slow and had massive CPU usage on Windows.

While researching it found this comment: https://github.com/arturadib/shelljs/blob/master/src/exec.js#L66-L68

We swapped ShellJS for a child_process.spawn() and so far it looks like we gained ~20% overall speed with a lot less CPU use.

No idea what is going on in that sync-hack but it is not a good solution, at least not on Windows.