J has the verbs behead[0] (for xs[1:]) and curtail[1] (for xs[:-1]), so the J oneliner for the above code would be

    <./ ([&}. - }:) xs 

[0] https://code.jsoftware.com/wiki/Vocabulary/curlyrtdot [1] https://code.jsoftware.com/wiki/Vocabulary/curlyrtco