TS is a good language that AS3 users would prefer, but it is new, there was Haxe but it does not has a giant behind it. I am not sure what is a good alternative

TS is a good language that AS3 users would prefer, but it is new, there was Haxe but it does not has a giant behind it. I am not sure what is a good alternative to Flex, React is the one that seems closer because you have a render function that you can implement and you have the markup but you are still missing a collection of built in, good quality components, I see a lot of projects wrapping in angular or React jQuery components(callendars, color pickers), In Flex you had this components and you could customize them with item renderers and you can extend them with inheritance.