def add_script_data(req, data={}, **kwargs):
    """Add data to be made available in javascript scripts as global variables.

    The keys in `data` and the keyword argument names provide the names of the
    global variables. The values are converted to JSON and assigned to the
    corresponding variables.
    """
    script_data = req.chrome.setdefault('script_data', {})
    script_data.update(data)
    script_data.update(kwargs)
