Reason's module vs JS Classes

00_object-example.js

// Example based on following tweet: https://twitter.com/housecor/status/1247497178882486272

// Class Example
class User {
  constructor(name, email) {
    this.name = name;
    this.email = email;
  }

  greet() {
    console.log(`Hi ${this.name}`);
  }

  contact() {
    console.log(`Emailing ${this.email}`);
  }
}

const cory = new User("Cory", "[email protected]");
cory.contact();

01_module-example.re

// In Reason, code is mainly structured in immutable record types (compiled to JS objects),
// functions and modules... it uses only a few features, but due to functional composition it's very easy
// to build more complex structures (encapsulation etc). Less to learn, more power to the user!

// Playground Link:
// https://reasonml.github.io/en/try?rrjsx=true&reason=LYewJgrgNgpgBAVQM4wE5wLxwN4Cg5wD0AVHAOrxgwBmAlgHYxhwCGcqMAxiKmADRwA7gAtanYQJD04nDiwAutKQMZM48kHGEsAbjHwEWUKK3nzUtAEYR5MJHAAOHFPXkA6D3CS1gtKC1QoAE91TTZOfyR7bnokcwhODXRiQgN5IId4eUwcAwJ6FmAYAC4vcwYAcz48uBhgFj9SuIt6KoMAXwBuAwMSOABRPVQg+VFW2qgUOFp7ACsIONY4agh6RKVpQVpRhjgQCHQAA2Q0Q7hQSFg8gElpahZEgR37LeNWN-MWWP9bUK8fBywZardZSGRGSasejMABSAGU9pZZlx5PZdqN4DBoXAUgZYNkKhwYNksBBMAA+OAwpBuKAgCoACgARAAJWhwJlwADUXLgEDcBSKAEpugQ8cSZFJ5A8SXyKVSaXTGUz+vU-JUOdzefy6g0oCLcF1cLg+gAVYTwOioRYKcrWX7HFCoAWFGBnWzGewYyXABx+NDqbTZQTwALwbTQqAatjpTJ5LY7aTek7oC7QeBIbiZHGpfGS4Y5PAEFMuoqlJkAYR4QSZ1QIusaHO4wwAAnJErNM1IkNBFK03NxgEzDd0TaR+gBHCC0HRGLHZDSIJ0DqUyhnNoJCjxuWpDEZjCrTOYLbJsFZrRRg3EbgC05JLMWliU6QA

module User = {
  // We defined a record, which, on creation, need to have
  // all attributes present... similarly to a class constructor
  type t = {
    name: string,
    email: string,
  };
  
  // Everything else is just a function within our `User` module
  // In fact, this will all translate to simple function calls and JS objects in the end
  let greet = u => Js.log("Hi " ++ u.name);
  
  let contact = u => Js.log("Emailing " ++ u.email);
};

// The first attribute `User.name` tells the compiler that we are handling a type
// within the User module scope
let cory = {
  User.name: "Cory",
  email: "[email protected]"
};

// Equivalent to User.contact(cory)... everything is just a function
cory->User.contact;

02_module-example.bs.js

// This is the compiled JS output for the `module-example` file

// Generated by BUCKLESCRIPT, PLEASE EDIT WITH CARE
'use strict';


function greet(u) {
  console.log("Hi " + u.name);
  return /* () */0;
}

function contact(u) {
  console.log("Emailing " + u.email);
  return /* () */0;
}

var User = {
  greet: greet,
  contact: contact
};

var cory = {
  name: "Cory",
  email: "[email protected]"
};

contact(cory);

exports.User = User;
exports.cory = cory;
/*  Not a pure module */