Catamorphism, fold, lazy evaluation, continuation, short circuiting, iteration

foldlk.js

const foldlk = f => acc => xs => {
  const next = (acc, key) => xs.length === key
   ? acc
   : f(acc) (xs[key], acc => next(acc, key + 1));

  return next(acc, 0);
};

const every = f => foldlk(x => (y, k) => f(y) ? k(true) : false) (true);
const some = f => foldlk(x => (y, k) => f(y) ? true : k(false)) (false);
const take = n => foldlk(acc => (x, k) => acc.length === n ? acc : (acc.push(x), k(acc))) ([]);

every(x => x % 2 === 0) ([2,4,6,8]); // yields true
some(x => x % 2 === 0) ([1,2,3,5]); // yields true and stops early
take(3) ([1,2,3,4,5]); // yields [1,2,3]