There has not been an air combat involving F-35s or J-20s or the T-50s, since all three aircraft are at various stages of development and there's not been a sufficient body of data to be able to run this thing through the simulators.
There is speculation as to what is intended to be done by these aircraft. For example, the suggestion is that the J-20's mission will be the forcing back of the United States Navy by being able to approach an American carrier battle group in this stealthy fashion, then carry a high-speed missile and drop it when they're within range of the carrier, and by this then being able to saturate the carrier's air defences. That seems to be the logical thinking that is currently going on in the People's Liberation Army.
On the Russian side, of course, the Sukhoi aircraft is intended to be a counter to the F-22 and therefore is being seen as an air superiority fighter whose job it is to secure the air, in which attack aircraft could then do various jobs.
The F-35 has not been run against either of these aircraft, so I can't give you an answer to that, but it certainly is a very legitimate question to ask.