TypeScript is essentially the “measure twice, cut once” approach to JavaScript.

Yeah, anything can be anything in JS and the type declarations don’t make it into the compiled JS, but allowing anything to be anything starts to become fairly dangerous when the size of your projects starts to grow and especially when you’re working with a team.

Rather than writing functions and just hoping they always get called with a parameter that has the properties you expect to use, TypeScript helps you make sure that you always are calling that function with the right object in the arguments. You don’t need to debug some runtime error up and down 8 frames in the call stack because this week you named a property “maxValue” but last week you used “maxVal” or you forgot to parseInt some string because you thought it would be coerced - you just need to make sure your types match and eliminate that type of debugging altogether.

All in all, TS really just enforces a bit of sanity to the foot gun that is vanilla JS.