DanShappir

const result = numbers
	.filter(v => v % 2 === 0) // retain only even numbers
	.map(v => v + 1) // increase these numbers
	.slice(0, 3); // get the first 3 items

DanShappir

const result2 = _(numbers)
	.filter(v => v % 2 === 0) // retain only even numbers
	.map(v => v + 1) // increase these numbers
	.slice(0, 3) // get the first 3 items
	.value();

DanShappir

function* map(src, op) {
  for (const value of src) {
    yield op(value);
  }
}

DanShappir

function* filter(src, op) {
  for (const value of src) {
	  if (op(value)) {
      yield value;
    }
  }
}

DanShappir

const result2 = Array.from(
  slice(
    map(
      filter(numbers, v => v % 2 === 0),
      v => v + 1
    ),
    0, 3
  )
);

DanShappir

function* slice(src, start, finish = Number.MAX_SAFE_INTEGER) {
	let index = 0;
  for (const value of src) {
    if (index >= finish) {
      break;
    }
    if (index >= start) {
      yield value;
    }
    ++index;

DanShappir

const result3 = numbers
  |> filter(#, v => v % 2 === 0)
  |> map(#, v => v + 1)
  |> slice(#, 0, 3)
  |> Array.from;

DanShappir

const retainOnlyNumeric = obj
  |> Object.entries
  |> filter(#, ([, value]) => typeof value === 'number') 
  |> Object.fromEntries;

DanShappir

const largeNumber = numbers
  |> filter(#, v => v > 42)
  |> slice(#, 0, 1)
  |> Array.from
  |> (a => a[0])(#);

DanShappir

function head(src) {
  for (const value of src) {
    return value;
  }
}