iter-fns

iter.js

function* map(f, iter) {
	for (const i of iter) {
		yield f(i);
	}
}

function* filter(f, iter) {
	for (const i of iter) {
		if (f(i)) yield i;
	}
}

function reduce(f, iter, acc) {
	for (const i of iter) {
		f(i, acc);
	}
	return acc;
}

function collect(iter) {
	const arr = [];
	for (const i of iter) {
		arr.push(i);
	}
	return arr;
}

console.log(
  collect(
    filter(x => x % 2 === 0,
      map(x => x + 1,
        [1, 2, 3, 4]
      ))));