Reason

Paradigms	Multi-paradigm: functional, imperative, modular, object-oriented
Family	ML: Caml: OCaml
Designed by	Jordan Walke
First appeared	May 16, 2016; 8 years ago (2016-05-16)[1]
Stable release	3.14.0[2]  / November 29, 2024; 56 days ago (November 29, 2024)
License	MIT
Filename extensions	.re, .rei
Website	reasonml.github.io
Influenced by
OCaml, JavaScript

Reason, also known as ReasonML, is a general-purpose, high-level, multi-paradigm, functional and object-oriented programming language and syntax extension and toolchain for OCaml created by Jordan Walke, who also created the React framework, at Facebook.^[3][4] Reason uses many syntax elements from JavaScript, compiles to native code using OCaml's compiler toolchain, and can compile to JavaScript using the ReScript compiler.^[5]

The Reason community officially provides ReasonReact as a solution for React-based web applications.^[6]

Reason was originally compiled to JavaScript using the BuckleScript compiler,^[7] which was created at Bloomberg L.P.

In 2020, the BuckleScript and Reason toolchain was rebranded to ReScript, essentially creating a separate language that had different syntax from Reason and only compiled to JavaScript.^[8]

BuckleScript was forked to Melange^[9] to continue to support compiling OCaml to JavaScript.

type schoolPerson = Teacher | Director | Student(string);

let greeting = person =>
  switch (person) {
  | Teacher => "Hey Professor!"
  | Director => "Hello Director."
  | Student("Richard") => "Still here Ricky?"
  | Student(anyOtherName) => "Hey, " ++ anyOtherName ++ "."
  };

• Elm – A functional language that uses an abstraction called ports to communicate with JavaScript
• PureScript – A strongly-typed, purely-functional programming language that compiles to JavaScript

Wikibooks has a book on the topic of: OCaml

• Official website
• Reason Project Organisation on GitHub
• ReasonReact