def minify_js(input_files, output_file):
    """
    Minifies the input javascript files to the output file.

    Output file may be same as input to minify in place.

    In debug mode this function just concatenates the files
    without minifying.
    """
    from .modules import minify, utils
    if not isinstance(input_files, (list, tuple)):
        raise RuntimeError('JS minifier takes a list of input files.')
    return {'dependencies_fn': utils.no_dependencies, 'compiler_fn': minify
        .minify_js, 'input': input_files, 'output': output_file, 'kwargs': {}}
