(1) I'm not sure I understand point. JS has long been without alternative, that's why JS has seen such a massive uptake. Moreover all JS alternatives, from Type

(1) I'm not sure I understand point. JS has long been without alternative, that's why JS has seen such a massive uptake. Moreover all JS alternatives, from TypeScript to Scala.js to Elm to Flow are adding types. Anyway JS's popularity is orthogonal to questions about efficient compilation. Types drastically simplify those, for you can work out at compile time how much memory needs to be allocated for each sub-expression of the program under execution. If you don't have types, you can only do that at run-time, and need extremely complicated JIT compiler technology to make this moderately performant. (2) Sure. Still extremely helpful, all the more so, the bigger the software. If you don't have types to do this, you will have to find those bugs by testing -- much more labour intensive. (3) Detached, maybe, but still true. To paraphrase Sutton's law: I'm detached from the toils of contemporary bread/butter programmers and look at verification because that's where the interesting open problems are.