Backward compatibility \"3ds\" and \"WiiU\" on \"Nintendo Switch\".

Please tell me whether Nintendo Switch backward compatibility? Wanted to buy it, but something with games there is generally a dead weight, and I thought that if there is backwards compatibility, then take it. I began to search for information and googled only some old Wikipedia for this reason(the time before the start of sales switch), and there was written that it will have compatibility, but only with digital copies of games. And the more I nor any mention of it is not found. I go now Nintendo market but there is not any 3ds or WiiU exclusives.