This was inspired by the JS-comint mode on sourceforge.
The shell does not, in itself, provide a mock DOM, and so is unsuitable, by itself, for running tests of browser-centric code. You couldn’t run jQuery in it, for example.
This module does have the ability to load in separate modules when you begin the shell. For example, you can load in json2.js, into the shell, or a module with extensions to the string prototype. You can see that in the screenshot above.