/**
 * Unique symbol to mark Frame instances.
 *
 * We use a symbol because in some cases importing the Frame to do
 * instanceof checks introduces circular references.
 *
 * Having the symbol in it's own file prevents any potential circular
 * references and allows checking if an object is a frame
 */ export const FRAME_SYMBOL = Symbol ( 'FRAME_SYMBOL' ) ; param object export function isFrame ( object ) { return object && object [ FRAME_SYMBOL ] === true ; }