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Java (via GWT) vs Haste

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When comparing Java (via GWT) vs Haste, the Slant community recommends Haste for most people. In the question“What are the best languages that compile to JavaScript? ” Haste is ranked 19th while Java (via GWT) is ranked 21st. The most important reason people chose Haste is:

Haste was designed to allow both the client and server to be written as parts of the same, type-safe application. This is in stark contrast to most other options, where the client and server are considered two separate entities, resulting in extra manual validation code and more chances for type errors.

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Common Questions

What are the best languages that compile to JavaScript?

Pros

Pro
Strongly typed, good tooling

That's Java, so it is strongly typed, and we can use fully the IDE: error detection, refactoring, auto-completion, etc.

Pro
Familiar for Java developers

Perfect if you have a strong background in Java programming, and need to code for the client side.

Pro
Fantastic IDEs

Because Java is statically typed, integrated development environments (IDEs) for Java can provide a lot more feedback on errors you will encounter. Java IDEs can give you specific errors in the location where they occur without having to run the code every time. This makes is faster to debug and learn from your mistakes.

IDEs also have extensive auto complete capabilities that can help you learn the programming libraries you are using faster and tell you what functions are available.

Pro
Most commonly used language in industry

Java is one of the most popular languages in industry, consistently ranking either first, or occasionally second (behind C or Javascript) in terms of usage. Polls (see sources below) show it to be consistently in high demand, particularly as measured by job board postings. This makes Java a great time investment, as you will be easily able to get a job utilizing your skills, particularly as those Java applications in production now will continue to need maintenance in the future. It also results in great support for tools and plenty of computer science books, example projects and online tutorials.

Pro
Consistent programming standards

Most Java code follows very standardized coding styles. This means that when you're starting out, there are fewer questions about how you should implement something as the programming styles and patterns are well established and consistent. This consistent style means that it's often easier to follow others' example code, and that it's more likely to meet at least a certain minimum standard of quality. This discipline with consistent stylistic standards also becomes useful later, when collaborating on projects with larger teams.

Pro
Highly optimized JavaScript

Produced JS is highly optimized, can be separated in modules with lazy loading, can be internationalized while loading only the chosen language.

Pro
Client and Server as the same application

Pro
Almost full power of Haskell

Haste supports the Haskell 2010 standard except for Template Haskell as well as most GHC extensions.

Pro
Automatic, type safe program slicing

Haste lets you write client and server as a single program, automatically generating code for the server as well as the client, giving you full type safety even across the Internet.

Pro
Generates small, reasonably performant code

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Cons

Con
Too verbose

A Hello world needs package, class, static method and the actual printf.
Reading a line from input requires instatiating 5 objects in the right order.
Exceptions are everywhere, particularly since all values are nullable.
Java has a getter/setter culture, but without native syntax support.
portable Java code lacks anonymous functions, and continues to lack good support for partial application, compensating instead with verbose design patterns, kludges like anonymous inner classes, or just inline code.
It is statically typed without type inference, with a culture that promotes long class names.
Poor support for sum-types and pattern matching leads to overuse of inheritance for dynamic dispatch and chains of nested conditionals

Especially for beginners, this can make reading Java code feel overwhelming; most Java courses tell students to simply copy, paste, and ignore a significant percentage of the code until they've learned enough to understand what it means.

For experienced programmers, this makes Java feel tedious, especially without an IDE, and actively discourages some solutions and some forms of abstraction.