Here’s the Deal

Ruby (via Opal) vs Ceylon

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When comparing Ruby (via Opal) vs Ceylon, the Slant community recommends Ceylon for most people. In the question“What are the best languages that compile to JavaScript? ” Ceylon is ranked 15th while Ruby (via Opal) is ranked 16th. The most important reason people chose Ceylon is:

It has a Web IDE: http://try.ceylon-lang.org/ with impressive demos: http://try.ceylon-lang.org/?gist=bd41b47f325b6d32514a so you can try it without installing anything, and see the JS generation / interop in action.

Specs

No specs yet!

Current stable version1.3.2

Ranked in these QuestionsQuestion Ranking

Common Questions

What are the best languages that compile to JavaScript?

Pros

Pro
Elegant syntax

Ruby has a very clean syntax that makes code easier to both read and write than more traditional Object Oriented languages, such as Java. For beginning programmers, this means the focus is on the meaning of the program, where it should be, rather than trying to figure out the meaning of obscure characters.

presidents = ["Ford", "Carter", "Reagan", "Bush1", "Clinton", "Bush2"]
for ss in 0...presidents.length
    print ss, ": ", presidents[presidents.length - ss - 1], "\n";
end

Pro
Popular

Ruby is one of the most popular languages for developing web sites. As a result, there's an abundant amount of documentation, sample code, and libraries available for learning the language and getting your project up and running. The most popular features are just 'gem install' away.

Pro
Try it out in the browser

Pro
Strong static typing, null safe and flexible, almost dynamic type system

The compiler prevents you from using a potentially null variable, unless you check it is not null. Ie. it forces you to check a potentially null value before using it.
The type system is strict, but flexible, allowing union and intersection of types, covariant and contravariant types, reified types, etc.
Type inference and union types allows a dynamic programming style, close of JS spirit.

Pro
Designed from the start to generate JavaScript

It brings type safety to JS, allowing to define interfaces to existing JS APIs, yet using the dynamic keyword for flexible calls in the JS ecosystem.

Pro
Excellent IDE support

Ceylon has reified generics, so it doesn't loose the type of collections at runtime. This makes autocompletion, debugging, etc. first-class. The Eclipse plugin makes it a full-fledged Ceylon IDE, and an IntelliJ IDEA plugin is in the works.

Pro
Great tutorial

Gavin King, main author of the language, has a great, clear technical writing style, making understandable difficult concepts like variance or sound type system.

Pro
Excellent documentation

The language specification is very complete and up to date; also, the language module is very well documented.

Pro
Javascript interoperability

Ceylon has special language-level support for interoperation with dynamically typed languages like JavaScript, and its module system even interoperates with npm.

Pro
Easy to learn even if you don't have prior programming experience

Ceylon is indeed fairly easy and readable. Of course those ones who know OOP and a bit of functional programming concepts will feel almost at home right from the start.

Pro
Generate HTML

HTML generation is supported right in the SDK.

Pro
Same code in backend and frontend

If you don't use platform-specific features, you can reuse the same code in your backend server (be it in Java or JavaScript) and in your client-side browser code, for example for storing data, validating input etc.

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Cons

Con
Meta-programming causes confusion for new developers

The ability for libraries to open classes and augment them leads to confusion for new developers since it is not clear who injected the functionality into some standard class.

In other words, if two modules decide to modify the same function on the same class can introduce a number of issues. Mainly, the order in which the modules are included matters. Since you more or less can't tell what kind of "helper" functions a module might write into any class, or for that matter, where the helper function was included from, you may sometimes wonder why class X can do Y sometimes but not at other times.

Con
Lack of physical or electronic books

We should hope Red Hat or anyone interested would take the time and write one. That would strengthen the maturity of the language, but Ceylon is rapidly developing which can make the author's efforts futile because his or hers work will become obsolete soon.
The second hindrance is, of course, popularity of the language which can't give much to the pockets of the author (however, Dart's unpopularity at start didn't prevent it to have a lot of printed material, but that's Google's child, we know).

Con
Currently has large runtime

Ceylon 1.2 needs a language runtime of 1.55 MiB, and the Collection library adds another 370 KiB. That's a lot for the Web...
Now, this has to be put in perspective: if you use Ceylon to make a web application, these files will be loaded once, then cached by the browser (that's not casual browsing).
Moreover, most servers compress such resource, and the numbers become respectively 234 KiB and 54 KiB, which is more reasonable...