def render(self, context):
        """
        Build the filepath by appending the extension.
        """
        module_path = self.path.resolve(context)
        if not settings.SYSTEMJS_ENABLED:
            if settings.SYSTEMJS_DEFAULT_JS_EXTENSIONS:
                name, ext = posixpath.splitext(module_path)
                if not ext:
                    module_path = '{}.js'.format(module_path)

            if settings.SYSTEMJS_SERVER_URL:
                tpl = """<script src="{url}{app}" type="text/javascript"></script>"""
            else:
                tpl = """<script type="text/javascript">System.import('{app}');</script>"""
            return tpl.format(app=module_path, url=settings.SYSTEMJS_SERVER_URL)

        # else: create a bundle
        rel_path = System.get_bundle_path(module_path)
        url = staticfiles_storage.url(rel_path)

        tag_attrs = {'type': 'text/javascript'}
        for key, value in self.tag_attrs.items():
            if not isinstance(value, bool):
                value = value.resolve(context)
            tag_attrs[key] = value

        return """<script{attrs} src="{url}"></script>""".format(
            url=url, attrs=flatatt(tag_attrs)
        )
Build the filepath by appending the extension.