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I disagree. `null` in TypeScript is equivalent to `None` in many other typed languages. `undefined` in Typescript is like null in other languages, with the cave

I disagree. `null` in TypeScript is equivalent to `None` in many other typed languages. `undefined` in Typescript is like null in other languages, with the caveat that if you’re working to transition an untyped codebase and trying to bring types, there may be a useful place for `undefined` in order to express that there is a lack of safety / strict-handling in that area. I’m still not sure about Error handling, though. Seems feasible that in a fully typed project, any possible unhandled error type could raise a compile error. AFAIK there’s nothing (beyond catch + exhaustive switch) to handle exhaustive error checking in TypeScript, nor is there lib support for handling it either.

remram 5y ago
Which language has both a "None" and "null"?
- efficax 5y ago
  javascript, at least, has "undefined" and "null", an infuriating duality of falsiness. PHP also has a notion of not being set as well as being set but null.
  - remram 5y ago
    JavaScript is what we are talking about in this thread, making the point that JavaScript is similar to JavaScript does not help ;-)
    - deleted 5y ago
      [deleted]
- mynameisash 5y ago
  Scala, as I recall. It encourages using Options (Some/None), but since it runs on the JVM and will often interop with Java libraries, you can also have nulls. Not exactly a language design, but an unfortunate reality.
  - remram 5y ago
    Oh no! Does it not have a type for NonNull references, like Rust does?
    - kaba0 5y ago
      Since Scala 3, it can have total static analysis where nulls become a separate type that has to be explicitly declared in type signatures. So, yes.