[fulafel]

I know only of Flow for JS, but are there signs that it's commonly used, or are there other JS typecheckers with a more optimistic trajectory?

It looks to me more like compile-to-JS languages are winning this race. Which is good, as it enables sthings like ClojureScript and Elm. Also many of us think the lack of static types is the least of the problems in JS.

[pvg]

Flow and TypeScript are used a fair bit and both have adoption in big organizations that make big, commonly used tools. I don't think any of the compile-to-JS languages have ever really got quite that far and I'm somewhat skeptical they will.

[fulafel]

Ah. I guess due to the superset-of-JS property you might kinda sorta see it as annotated JS, though it has its own syntax and has to go through a compiler to produce runnable JS.

edit: Seems the TS tools also have JS linting functionality, where you put JSDoc annotations in comments and use the new --checkJs options, I guess you may have meant this too.