def py2js(v):
    """Note that None values are rendered as ``null`` (not ``undefined``.

    """
    # assert _for_user_profile is not None
    # logger.debug("py2js(%r)",v)
    for cv in CONVERTERS:
        v = cv(v)

    # if isinstance(v,LanguageInfo):
        # return v.django_code

    if isinstance(v, Value):
        return v.as_ext()
        # v = v.as_ext()
        # if not isinstance(v, basestring):
            # raise Exception("20120121b %r is of type %s" % (v,type(v)))
        # return v
    if isinstance(v, Promise):
        # v = force_text(v)
        return json.dumps(force_text(v.encode('utf8')))

    if isinstance(v, types.GeneratorType):
        return "".join([py2js(x) for x in v])
    if etree.iselement(v):
        return json.dumps(etree.tostring(v))

    # if type(v) is types.GeneratorType:
        # raise Exception("Please don't call the generator function yourself")
        # return "\n".join([ln for ln in v])
    if callable(v):
        # print 20120114, repr(v)
        # raise Exception("Please call the function yourself")
        return "\n".join([ln for ln in v()])
    if isinstance(v, js_code):
        return str(v.s)  # v.s might be a unicode
    if v is None:
        # return 'undefined'
        return 'null'
    if isinstance(v, (list, tuple)):  # (types.ListType, types.TupleType):
        elems = [py2js(x) for x in v
                 if (not isinstance(x, VisibleComponent))
                 or x.get_view_permission(_for_user_profile)]
        return "[ %s ]" % ", ".join(elems)

    if isinstance(v, dict):
        # 20160423: removed "sorted(v.items())" because it caused
        # TypeError when the dictionary contained a mixture of unicode
        # and future.types.newstr objects.
        try:
            items = [
                i for i in sorted(v.items())
                if (not isinstance(v, VisibleComponent))
                or v.get_view_permission(_for_user_profile)]
        except __HOLE__ as e:
            raise TypeError("Failed to sort {0} : {1}".format(v, e))
        return "{ %s }" % ", ".join(
            ["%s: %s" % (py2js(k), py2js(i)) for k, i in items])

    if isinstance(v, bool):  # types.BooleanType:
        return str(v).lower()
    if isinstance(v, Quantity):
        return '"%s"' % v
    if isinstance(v, (int, decimal.Decimal, fractions.Fraction)):
        return str(v)
    if isinstance(v, IncompleteDate):
        return '"%s"' % v.strftime(settings.SITE.date_format_strftime)
    if isinstance(v, datetime.datetime):
        return '"%s"' % v.strftime(settings.SITE.datetime_format_strftime)
    if isinstance(v, datetime.time):
        return '"%s"' % v.strftime(settings.SITE.time_format_strftime)
    if isinstance(v, datetime.date):
        if v.year < 1900:
            v = IncompleteDate(v)
            return '"%s"' % v.strftime(settings.SITE.date_format_strftime)
        return '"%s"' % v.strftime(settings.SITE.date_format_strftime)

    if isinstance(v, float):
        return repr(v)
    # return json.encoder.encode_basestring(v)
    # print repr(v)
    # http://docs.djangoproject.com/en/dev/topics/serialization/
    # if not isinstance(v, (str,unicode)):
        # raise Exception("20120121 %r is of type %s" % (v,type(v)))
    return json.dumps(v)
    # try:
    #     return json.dumps(v)
    # except TypeError as e:
    #     raise TypeError("%r : %s" % (v, e))
    # return json.dumps(v,cls=DjangoJSONEncoder) # http://code.djangoproject.com/ticket/3324
dataset/ETHPy150Open lsaffre/lino/lino/utils/jsgen.py/py2js