Trade-offs in designing a new JavaScript type system

José Valim, who helped develop Elixir’s type system, says a new JavaScript type system might struggle to express every idiom precisely. For unsupported idioms, he outlines three choices: develop and prove new theory, reject them at a cost to compatibility, or fall back to dynamic typing. The fallback can limit further static checks, risk runtime mismatches or require runtime checks that may affect performance. He adds that Elixir’s strong-arrows approach may not suit JavaScript.