This isn't like using Kotlin or Scala in order to use an alternative to the "original" language. The power of TypeScript is that it is designed to be less an al

This isn't like using Kotlin or Scala in order to use an alternative to the "original" language. The power of TypeScript is that it is designed to be less an alternative programming language per se than a dev tool for JavaScript. Instead of choosing different semantics, you're being somewhat more explicit in specifying your JS semantics. And you aren't switching to a different ecosystem, you're making your tools more powerful when working with the JS ecosystem. Since the nature of this "tool" is an extension to the syntax, there is a bit of risk that there will be an conflict with some future JS, but other than that, the 2-factor (same but more explicit semantics, same but fortified ecosystem) analysis seems to show why TypeScript is popular.