[lgas]

> A note; typescript does nothing to ensure types are correct at runtime. Especially in the browser. You need to do runtime checking even if you're using typescript.

I'm not sure I understand - in what situation would you need runtime type checking? I always assumed the situation was similar to Haskell where the types are erased at runtime but it's still impossible (absent opting in to unsafe stuff) to have type errors at runtime.

[ehutch79]

As the other commenter said, ingesting data from various sources. You don't actually know what's in that JSON.

There's also a myriad of ways to alter data running in a browser. From plugins to just fooling around with the console in DevTools.

On a large enough team, you might not be able to trust the code calling your code. It's easy to slip 'as whatever' in there. I do it when using vue's reactive objects instead of fighting with typescript.

[treflop]

Usually ingesting external data.

You NEED to verify data from outside your app anyways but if you have runtime checking, trying to cheat and skip that step is harder.