TypeScript generates some code that's unlike what a person would write directly in JavaScript, which probably does impact performance to some degree. Enums can

TypeScript generates some code that's unlike what a person would write directly in JavaScript, which probably does impact performance to some degree. Enums can become integers where a human might decide strings are good enough and more readable than magic numbers. And if you're only using TypeScript, you can avoid writing some run-time sanity checks. But it also emits a lot of boilerplate for modules and classes and such. Not sure if the net effect would be a gain or loss.