Test that DOMRect has a serializer On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS rect.__proto__ is DOMRect.prototype PASS toJSONDescriptor.value is an instance of Function PASS toJSONDescriptor.enumerable is true PASS toJSONDescriptor.configurable is true PASS toJSONDescriptor.writable is true PASS jsonObject = rect.toJSON() did not throw exception. PASS jsonObject.top is rect.top PASS jsonObject.right is rect.right PASS jsonObject.bottom is rect.bottom PASS jsonObject.left is rect.left PASS jsonObject.width is rect.width PASS jsonObject.height is rect.height PASS parsedJSONObject = JSON.parse(JSON.stringify(rect)) did not throw exception. PASS parsedJSONObject.top is rect.top PASS parsedJSONObject.right is rect.right PASS parsedJSONObject.bottom is rect.bottom PASS parsedJSONObject.left is rect.left PASS parsedJSONObject.width is rect.width PASS parsedJSONObject.height is rect.height PASS successfullyParsed is true TEST COMPLETE