function stringifyCheck( obj ) {
	var bool;
	try {
		JSON.stringify( obj );
		bool = false;
	} catch ( err ) {
		bool = err.message === 'Converting circular structure to JSON';
	}
	return bool;
}
Tests if an object contains a circular reference by trying to stringify the input object.

@private
@param {Object} obj - object to test
@returns {boolean} boolean indicating whether object contains a circular reference