This code will walk the path backwards looking for the proper javascript checker in each directory until it hits the root. Currently only supporting jscs and jshint as a fallback.

syntastic_javascript_checkers.vimrc

" jscs returns exit code when no config file is present
" if it does not exist, we use jshint
function! DetectSyntasticJavascriptChecker()
  let stack = split(getcwd(), '/')
  let len   = len(stack)

  while len >= 0
    let len  = len - 1
    let path = '/' . join(stack[0:len], '/')
    if (filereadable(path . '/.jscsrc'))
      return ['jscs']
    endif
  endwhile

  return ['jshint']
endfunction
let g:syntastic_javascript_checkers=DetectSyntasticJavascriptChecker()