def is_js_file(filename):
    """
    Return true if the filename ends in .js and is not a packed or
    minified file (no '.pack' or '.min' in the filename)

    >>> is_js_file('jquery.min.js')
    False
    >>> is_js_file('foo.json')
    False
    >>> is_js_file('ui.combobox.js')
    True

    """
    return filename.endswith('.js') \
       and not '.pack' in filename \
       and not '.min' in filename