Crystal vs. Haskell vs. JavaScript vs. PureScript Comparison Chart

Every expression in Haskell has a type that is determined at compile time. All the types composed together by function application have to match up. If they don't, the program will be rejected by the compiler. Types become not only a form of guarantee, but a language for expressing the construction of programs. Every function in Haskell is a function in the mathematical sense (i.e., "pure"). Even side-effecting IO operations are but a description of what to do, produced by pure code. There are no statements or instructions, only expressions that cannot mutate variables (local or global) nor access state like time or random numbers. You don't have to explicitly write out every type in a Haskell program. Types will be inferred by unifying every type bidirectionally. However, you can write out types if you choose, or ask the compiler to write them for you for handy documentation.

PureScript is a strongly typed, purely functional programming language that compiles JavaScript. It enables developers to build robust web applications, web servers, and mobile apps using functional programming techniques. PureScript offers features such as algebraic data types, pattern matching, row polymorphism, extensible records, higher-kinded types, type classes with functional dependencies, and higher-rank polymorphism. The language emphasizes strong static typing and pure functions, ensuring code reliability and maintainability. Developers can compile PureScript code into readable JavaScript, facilitating seamless integration with existing JavaScript codebases. The ecosystem includes an extensive collection of libraries, excellent tooling, and editor support with instant rebuilds. An active community provides numerous learning resources, including the PureScript book, which offers practical projects for beginners.