I used jDojo (by IBM Rational) and it was great. It's a similar transpiler Java->JavaScript, with support for the Dojo Toolkit. One cool thing is that it's very easy and fast to define your own stubs for whatever library you are using, e.g. I added stubs for most of CKEditor and it was painless. The resulting output looks pretty much 1:1 like the Java code, which makes it easy to debug. Unfortunately their website is not viewable without an account:
https://jazz.net/wiki/bin/view/Main/JDojo
Twitter: https://twitter.com/jdojo
GWT is a very different beast, it's more of a framework with widgets and everything. When I tried it (a few years ago) the resulting JavaScript looked nothing like the Java code. If the Java code you write looks almost identical to the native JavaScript produced you don't really lose much, but you can refactor more easily etc.
GWT is not a transpiler only. It is a framework. In GWT, the transpiler part is so little that it would be totally wrong to assume that transpilers are wrong because GWT is wrong. JSweet is like TypeScript. It just adds typing. No runtime, no lib, no framework, just a transpiler: I don't see any issues except if you consider that typing is an issue.
Agreed. Transpilers are saving you nerves initially at the expense of making you want to commit suicide later. Like when you need to debug in real time, or check underlying "native" objects, or when a library the transpiler is relying on has a bug.
IMO transpilers are a Faustian deal. That's what my experience has taught me, your mileage may vary of course.
I disagree. I have been developing an IONIC application with JSweet. My experience is that when I want to refactor the code (for example, just renaming the data objects because the customer changes its mind about how to name something), then you are happy to have JSweet and you can make the code up-to-date in no time. The more the application gets complex, the better it is to have a transpiler to help you update your code safely. Your Faustian deal applies more to JavaScript IMO. It is very cool at the beginning, but at some point you start wondering what happens in your code and you need to write it again from scratch because it is not maintainable any more. JSweet is not GWT. It you don't like Java, try at least TypeScript and I am pretty sure you will change your mind.
I know nothing about JSweet but I have a 7-8 years of Java background and I can tell you right now that nothing in the Java world is a magic bullet.
But I am not here to argue specific examples. Sure, I definitely agree with you that Javascript is the worst offender in the transpiler world. I do however not see the connection between using a transpiler and having it easy when refactoring. If you mean that the transpiled language has an easier to parse AST and is thus much more prone to automated refactoring (Eclipse's "Rename Method" for example), I won't argue that; I know it can be true.
Nothing of what I said will stop me from trying Elm (transpiled to JS) for a hobby project though.
JSweet is not a magic bullet in the Java world, because JSweet is not Java. JSweet borrows the Java syntax to have well-typed JavaScript. Of course, not all transpilers have a focus on typing and not all of them have great tooling to back refactoring (not only renaming... you have plenty of other kind of help you will get when using a good Java IDE). But the focus of JSweet is typing and tooling (through Java).
I think that Christian Maioli Mackeprang is right. Some languages focus on instant productivity. They are really good and powerful to sketch a program in a few lines of code. But this quality comes at the expense of other important features that are really important for a language/development environment. People need to consider this or we will end up with poor programming environments and languages that are great for prototyping, but that don't scale up for complexity...