Here’s the Deal

Parenscript vs PureScript

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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 8th while Parenscript is ranked 33rd. The most important reason people chose PureScript is:

Has Typeclasses and RankNTypes

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Common Questions

What are the best languages that compile to JavaScript?

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
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
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
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
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
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
Awesome web frameworks

Thermite (React)
Halogen (VDOM, similar to ELM)
And hit these up with Signals, Isolated/(Managed?) Components, powerful functions and FFI

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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
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.