> There's no native typescript runtime. A proposal was actually floated recently to grandfather in TypeScript-like annotations[1]. It would be ignored by the r

> There's no native typescript runtime. A proposal was actually floated recently to grandfather in TypeScript-like annotations[1]. It would be ignored by the runtime and treated purely as a comment, and would be optional. This is what native runtime support for TypeScript would look like. Not sure if it will ever gain official support in the language though. > it doesn't enforce types at runtime, only at build time Runtime type "enforcement" is just your program breaking, for example "undefined is not a function". Well, I guess it isn't so simple, because JS does a lot of implicit type translation behind the scenes, like helpfully converting "123" to 123. It would be possible to "enforce" types at runtime by turning off that language feature in certain situations, but I don't think it will happen, for back-compat reasons. [1] https://github.com/tc39/proposal-type-annotations https://github.com/tc39/proposal-type-annotations