What does xhr send do when there is no connection from device to the network

Hello,

I have an application which has an bigger sync process, via RPC/JSON.

Cause of the huge data volume ~50 MB, the initial sync is only allowed via wifi.

Simulate an connection lost by turning my MAC's wifi of, cause that the last executed communication by the xhr object ends in "oSuccess" with status 200 instead of an "onError" callback.

For me it seems that xhr.send does not have any effect, there is no state for this case and no callback either.

Android 4.4 and iOS 7-8 having the same behavior.

Does anybody know how to handle reliable this case?