javascript - What is going on in this code ? I do not understand how this works could someone please step me through this

Question

Can someone please explained the steps that are happening in this code particularly the marked part. Is it recursive how does it slot together..?

const func = x => k => func (k (x))
//                     ^^^^^^^^^^^^      
const add = x => y =>
  x + y

func(1)(add(2))(add(2))(console.log);

Answer 1

As it stands, func doesn't type check because we can't construct the infinite type t a ~ (a -> b) -> t b. However, we can get around that restriction by creating a new data type as follows.

// Chain :: (forall b. (a -> b) -> Chain b) -> Chain a
const Chain = chain => ({ chain });

// func :: a -> Chain a
const func = x => Chain(k => func(k(x)));

// add :: Number -> Number -> Number
const add = x => y => x + y;

// trace :: a -> a
const trace = x => {
    console.log(x);
    return x;
};

// Chain Number
func(1).chain(add(2)).chain(add(2)).chain(trace);