A FE is expected to know enough of the language in the backend that they can integrate a design without having to bother a programmer for help; the various ways

A FE is expected to know enough of the language in the backend that they can integrate a design without having to bother a programmer for help; the various ways to echo content, how to tap into helpers and make your own, etc. Seems rather obvious but a lot of FE people think that if a line is written in Java or Ruby then they aren’t responsible for it. Also important for FE to know their core languages, irrespective of popular abstractions they will probably end up using (JS and jQuery or CoffeeScript, CSS and SASS or LESS, etc.). Again obvious but these days a lot of people working front-end will claim they know JavaScript, when they actually mean they know jQuery and drown when tasked to work on a project not using a library or something else.