> One has to be fluent with reading type definitions thus have good understanding of the type syntax. I must admit, from time to time I could not make sense of

> One has to be fluent with reading type definitions thus have good understanding of the type syntax. I must admit, from time to time I could not make sense of them easily when reading declaration files from third parties. That makes sense when comparing it to other languages, but compared to JavaScript: those type definitions are a pure bonus? In other words, if they'd have been written in JavaScript you'd still have to make sure to pass in the correct data, but you'd have only the documentation to guide you there. (Of course, if you yourself are using TypeScript, you do have to know how to make sure that TypeScript knows that you're passing in the correct data. But the flip side is that the more complex types will allow for better inference that helps your editor to provide better guidance on how to give it the correct data.)