Implementing array functions as generators

array_generators_util.js

const log = console.log;

function map(fn) {
  return function* (arr) {
    for (const el of arr) {
      yield fn(el);
    }
  }
}

function filter(fn) {
  return function* (arr) {
    for (const el of arr) {
      if (fn(el)) {
        yield el;
      }
    }
  }
}

function pipe(...args) {
  return function (arr) {
    let r = arr;
    for (const fn of args) {
      r = [...fn(r)];
    }
    return r;
  }
}

const evenSquares = pipe(
  filter(n => n % 2 === 0),
  map(n => n * n),
);

log(evenSquares([1, 2, 3, 4])); // [4, 16]

const oddCubes = pipe(
  filter(n => n % 2 !== 0),
  map(n => n * n * n),
);

log(oddCubes([1, 2, 3, 4])); // [1, 27]