list2.js

const cons = (a, b) => (
  (idx) => {
    if(idx === 0) {
      return a;
    } else if(idx === 1) {
      return b;
    } else {
      throw "invalid index";
    }
  }
);

const car = (c) => c(0);
const cdr = (c) => c(1);

const isNil = (c) => car(c) === undefined && cdr(c) === undefined;

const reduce = (f, init, items) => {
  const iter = (items, acc) => {
    if(isNil(items)) {
      return acc;
    } else {
      return iter(cdr(items), f(car(items), acc));
    }
  };

  return iter(items, init);
};

const reverse = (items) => (
  reduce(cons, cons(), items)
);

const list = (...items) => (
  reverse(items.reduce((acc, x) => (
     cons(x, acc)
  ), cons()))
);

const listRec = (head, ...tail) => {
  return cons(
    head,
    tail.length === 0 ? cons() : listRec(...tail)
  )
}

const listIter = (...items) => {
  let ret = cons();
  items.forEach(x => ret = cons(x, ret));
  return ret;
};

const map = (f, items) => (
  reverse(reduce((x, acc) => cons(f(x), acc), cons(), items))
);

const filter = (f, items) => (
  reverse(reduce((x, acc) => f(x) ? cons(x, acc) : acc, cons(), items))
);

////////////////////////////////////////////////////////////
// Helpers
////////////////////////////////////////////////////////////

const inc = x => x + 1;

const even = x => x % 2 == 0;
const odd = x => x % 2 == 1;