[jitl]

98% of typescript compilation is just dropping the type annotations; Babel for example outputs TS almost exactly as written. There’s no voodoo compiler passes going on unless you add them on top of Typescript. There’s no practical performance difference from JSDOC comments unless you’re using tsc to target ES5 or below; and in that case vanilla ES2020 would need a similar amount of Babel shenanigans to downlevel iteration.