This provides a vagrant box with a pre-booted ghcjs running with ghc 7.10.1.

git clone https://github.com/joelburget/ghcjs-box.git
cd ghcjs-box
make up

This will download the vagrant box and start it, so all you need to do is:

vagrant ssh
cd /vagrant

Now you're inside the machine, sharing the ghcjs-box directory, with access to ghcjs.

Because ghcjs takes a long, long time to boot. And it's fragile. Using this ghcjs-box sidesteps that process, giving you a machine that's known to work.