HypeScript: Simplified TypeScript type system in TypeScript's own type system(github.com)

  type foo = {
     bar: "Vodka"
  }

  function doTheThing(color: "RED" | "GREEN") {
      //do stuff
  }

  doTheThing("RED"); //ok
  doTheThing("GREEN"); //ok
  doTheThing("ORANGE"); //doesn't compile, because the type of the param *isn't* string, it's "RED" | "GREEN"

  type Mountain = { name: "EVEREST", height: 8848 } | { name: "K2", height: 8611 };

    type Event = 'onClick' | 'onHover'

    // some stringly typed javascript can now be nicely typed
    something.triggerEvent('onClick', someData)

  interface TypeScript {
    typeScript: TypeScript;
  }