Monad example.

monad-example.js

// https://hackernoon.com/functional-javascript-functors-monads-and-promises-679ce2ab8abe
const Thing = value => ({
  value,
  map: morphism => Thing(morphism(value)),
  flatMap: morphism => morphism(value)
})

const thing1 = Thing(1)                          //=> Thing (1)
const thing2 = thing1.flatMap(x => Thing(x + 1)) //=> Thing (2)

/*

Sometimes functions return a value already wrapped. This could be inconvenient to use with a Functor because it will re-wrap the Functor in another Functor.

const getThing = () => Thing(2)const thing1 = Thing(1)thing1.map(getThing) //=> Thing (Thing ("Thing 2"))
This behavior is identical to Array's behavior.

const doSomething = x => [x, x + 100]
const list = [1, 2, 3]list.map(doSomething) //=> [[1, 101], [2, 102], [3, 103]]

*/

/*

A Functor is something that is Mappable or something that can be mapped between objects in a Category.
A Monad is similar to a Functor, but is Flat Mappable between Categories.
flatMap is similar to map, but yields control of the wrapping of the return type to the mapping function.
A Promise breaks the Functor and Monad laws, but still has a lot of similarities. Same same but different.

*/