Javascript animation issue

I have seen this animation on android and I have done a mental project to how to do it in javascript.What I don't understand is how to select the previous "card" and the next "card" to apply them animation when the card that is moving "touches" the edges of his father.Have you got any ideas?

https://drive.google.com/file/d/0B6zPGxCIHPIjbVRHU19xSFVNUDg/view?usp=drivesdk