[jaequery]

what is scary about all these TypeScript, PureScript, Elm, etc, is that for variety of reasons, any one of these can just come and go. coffeescript anyone?

i'd tread very carefully and wisely before choosing any one of these paths.

it only makes sense imo if you come from Haskell, Clojure, or some other ML background to have an explicit interest in these languages.

[iLemming]

Coffeescript did not offer anything but different syntax. It hasn't improved the semantics of the language. Some people liked it and some didn't.

Elm, PureScript, and Clojurescript are fundamentally different languages. Javascript today has bloated, and it keeps growing. Experienced developers tend to dislike it. Newbie developers struggle with it. It is no longer "a small language with a low entry barrier". ECMAScript specification is already bigger than Java's.

PLs of today and the next couple of decades will be striving for optimizing for programmer's productivity, performance, or correctness of the program. Javascript today does not fit in any of these categories. So it is only natural - the trend of using alt-js langs will only grow.

[recursive]

Typescript is essentially just javascript with types. The compiler just checks and then takes the types out. So with typescript, if you need to migrate away, you just take your compiler output, and ditch your .ts files. The output is generally just as readable as the input.