Narwhal, Tusk, and Sea
Narwhal is your JavaScript interpreter. It is executable with narwhal or js. See narwhal --help for a list of its options. It is comparable to your shell, Python or Ruby/IRB.
Tusk is your package manager. Tusk by default installs packages whereever narwhal is installed. See tusk help for a list of options. It is comparable to apt or gem. You can also use tusk to create new “packages”, application project scaffolds, or “virtual environments”, which are all share a common structure.
sea is a tool for entering a Narwhal “virtual environment”. It executes a command or reexecutes your shell inside a “virtual environment”. There is a version of sea that comes packed with “Narwhal”, that you can use to “enter” your system narwhal environment, which is handy if narwhal/bin is not on your path. You can also source bin/activate, as long as your version of bash supports the ${BASH_ARGV[0]} notation, or if your current working directory contains bin/activate.
You can use narwhal, tusk, and sea to create multiple, independent, reproducable Narwhal project installations. Assuming that narwhal and tusk are on your path, you can use tusk init to create two application projects.
$ tusk init foo
$ tusk init bar
$ cd foo
foo$ bin/sea
PATH=foo/bin
SEALVL=1
foo$ tusk install jack
foo$ edit jackconfig.js
foo$ jackup
Loading configuration module at foo/jackconfig
Jack is starting up using Simple on port 8080
^C
foo$ echo $SEA
foo
foo$ which sea
foo/bin/sea
foo$ exit
SEALVL=0
foo$ cd ../bar
bar$ bin/sea
PATH=bar/bin
SEALVL=1
...When you are in a Sea, Narwhal loads all of the packages installed in that Sea and Tusk installs packages in your Sea. While you can manipulate the NARWHAL_PATH and JS_PATH environment variables manually, Seas obviate the need.
Each sea can also have a different JavaScript engine. Edit narwhal.conf in your Sea to use a different engine.
$ js -e 'print(system.engine)'
rhino
$ cat bar/narwhal.conf
NARWHAL_DEFAULT_PLATFORM=v8
$ bar/bin/sea 'js -e "print(system.engine)"'
v8
PATH=/bin
SEALVL=0