Simple intersection observer test with no explicit root and target in an iframe. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS entries.length is 0 PASS entries.length is 0 PASS entries.length is 1 PASS entries[0].boundingClientRect.left is 18 PASS entries[0].boundingClientRect.right is 118 PASS entries[0].boundingClientRect.top is 468 PASS entries[0].boundingClientRect.bottom is 568 PASS entries[0].intersectionRect.left is 18 PASS entries[0].intersectionRect.right is 118 PASS entries[0].intersectionRect.top is 510 PASS entries[0].intersectionRect.bottom is 568 PASS entries[0].rootBounds.left is 0 PASS entries[0].rootBounds.right is 785 PASS entries[0].rootBounds.top is 0 PASS entries[0].rootBounds.bottom is 600 PASS entries[0].target is [object HTMLDivElement] PASS entries.length is 2 PASS entries[1].boundingClientRect.left is 18 PASS entries[1].boundingClientRect.right is 118 PASS entries[1].boundingClientRect.top is 568 PASS entries[1].boundingClientRect.bottom is 668 PASS entries[1].intersectionRect.left is 0 PASS entries[1].intersectionRect.right is 0 PASS entries[1].intersectionRect.top is 0 PASS entries[1].intersectionRect.bottom is 0 PASS entries[1].rootBounds.left is 0 PASS entries[1].rootBounds.right is 785 PASS entries[1].rootBounds.top is 0 PASS entries[1].rootBounds.bottom is 600 PASS entries[1].target is [object HTMLDivElement] PASS successfullyParsed is true TEST COMPLETE