I don't want them to "learn JS." Most likely the person in question is trying to write web applications, and I want them to learn what is most useful for that. After writing web applications for years without TypeScript and then for years with it, I cannot imagine going back. I can make complex refactors with very little worry. Thanks to type inference, most of the TypeScript code I write is indistinguishable from JavaScript, so the idea that learning TS takes away from learning JS is ridiculous. When I suggested that the extra syntax might be distracting at first, I meant for like... a week.