Ranked in these QuestionsQuestion Ranking
Pro Higher kinded types
Has Typeclasses and RankNTypes
Pro Modules can be compiled to CommonJS
Pro High performance FFI code
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.
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 Pure functional language
You cannot have side effects, unless a function is explicitly defined as so.
Pro Awesome web frameworks
Halogen (VDOM, similar to ELM)
And hit these up with Signals, Isolated/(Managed?) Components, powerful functions and FFI
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
Con Slow compilation
On large project, for example Halogen