Is there any way to make a function's return accessible via a property?

Question

I'm a JS dev, experimenting with functional programming ideas, and I'm wondering if there's anyway to use chains for synchronous functions in the way the promise chains are written.

For example:

function square (num) {
  return num * num;
}
let foo = 2 
let a = square(foo) //=> 4
let b = square(square(foo)) //=> 16

Fair enough, but what I'd like to do (often to make code parsing easier) is to chain together those methods by passing that in as the first parameter of a chain. So that something like this would work:

let c = square(foo)
          .square()
          .square() //=> 256

Is there any way to do this with vanilla javascript, or is this something I'd have to modify the Function.prototype to do?

Answer 1

You might be interested in the Identity functor – it allows you to lift any function to operate on the Identity's value – eg, square and mult below. You get a chainable interface without having to touch native prototypes ^_^

const Identity = x => ({
  runIdentity: x,
  map: f => Identity(f(x))
})

const square = x => x * x

const mult = x => y => x * y

let result = Identity(2)
  .map(square)
  .map(square)
  .map(square)
  .map(mult(1000))
  .runIdentity
  
console.log(result)
// 256000