When comparing Parenscript vs PureScript, the Slant community recommends PureScript for most people. In the question“What are the best languages that compile to JavaScript? ” PureScript is ranked 6th while Parenscript is ranked 30th. The most important reason people chose PureScript is:
Has Typeclasses and RankNTypes
Question Ranking
Pros
Pro It is Common Lisp
Lisps are easy languages to learn (once you get past the parens) and Common Lisp is a very practical dialect.
Pro Run almost identically on both the browser and server
Parenscript code can run almost identically on both the browser (as JavaScript) and server (as Common Lisp).
Pro Higher kinded types
Has Typeclasses and RankNTypes
Pro Has row polymorphism and extensible effects
Pro Type safety
Compiling should be your first unit test. A tight type system (static and hopefully strong) will catch many logic errors that are often difficult to spot through debugging. In languages like PureScript, if it compiles, it often runs properly.
Pro Modules can be compiled to CommonJS
Modules compiled to CommonJS can be included with 'require', making it incredibly simple to call Purescript code from Javascript.
Pro High performance FFI code
The Eff monad, which is used for FFI code, optimizes out calls to bind, and supports tail call optimization, resulting in clean, efficient Javascript. The psc compiler also specifically recognizes the ST monad, and transforms scoped variables into mutable Javascript variables, for even more efficient code.
Pro Thorough documentation
The Purescript website has fairly thorough documentation for all of the language's features, and the Purescript blog contains several examples of practical usage.
Pro Pure functional language
You cannot have side effects, unless a function is explicitly defined as so.
Pro FFI
FFI system is quite good and easy to use. You can import functions curried or not curried. Records and arrays use native JS objects and arrays.
Pro Awesome web frameworks
Thermite (React)
Halogen (VDOM, similar to ELM)
And hit these up with Signals, Isolated/(Managed?) Components, powerful functions and FFI
Cons
Con The syntax may be hard to learn
Being an implementation of Lisp, Parenscript's syntax may seem cryptic and hard to understand for people not used to it. While Lisp has very little syntax compared to other languages and it's generally considered pretty terse, there's still an initial overhead in learning the language.
Con Lots of dependencies needed to get started
Purescript is written in Haskell, but meant to be used with Node.js. As a result, to get started , users must install ghc, cabal, node.js, grunt, and bower. Purescript also has its own compiler, and different semantics form Haskell, and so even after installing, there's still some overhead to getting productive with Purescript.
Con Lack of good IDE/tooling support
Con Slow compilation
On large project, for example Halogen
Con Restrictive FFI
Functions exported are all curried, and must be called as such from Javascript. The FFI syntax for importing Javascript functions, while slightly simpler and more readable than UHC/Fay's, means that calls to methods on objects must be wrapped to pass the object explicitly as a parameter.