If you have an native (non-javascript) object that has been bound to a Javascript object, this is where the link between the two is stored. Basically on the C

If you have an native (non-javascript) object that has been bound to a Javascript object, this is where the link between the two is stored. Basically on the C side of the bindings, when a native function is called, you receive the "this" object, and you can simply call JSObjectGetPrivate() to retrieve a pointer to the corresponding native object - assuming that you have previously called JSObjectSetPrivate...