functional-js-05.js

const Maybe = val => ({
  val,
  fmap(f) {
    if(this.val === null) return Maybe(null);
    return Maybe(f(this.val));
  }
});

// lets create some containers with our Maybe factory
let user = Maybe("Slacker George McFly");
let noUser = Maybe(null);

console.log(user.val);    // "Slacker George McFly"
console.log(noUser.val);  // null