as a web developer you must know have to deal with either javascript or coffee script. Full stack means you can both do frontend, backend, and also deploy. Not that you're expert in three but you're capable of getting the job done.
I just didn't want to put coffee script out of the scene. obviously to do frontend you must know the basics: css, html, js. but is well known that now there are some fancy pseudo languages that improve the lack of the basic ones, such as less/stylus/sass for css, and coffee script for javascript.
