// Multiple filters over a list O(2n)

const things = ['apple', 'orange', 'cat', 'dog'];

const animals_filtered = things.filter(item => item === 'cat' || item === 'dog');
const fruit_filtered = things.filter(item => item === 'apple' || item === 'orange');

// One reduce over list O(n):

const {animals, fruit} = things.reduce((curr, item) => {
  console.log('Item', item);
  if (item === 'cat' || item === 'dog') {
    curr.animals.push(item);
  }

  if (item === 'apple' || item === 'orange') {
    curr.fruit.push(item);
  }
  return curr;
}, { animals: [], fruit: []});

console.log('Animals:', animals_filtered, '&', animals);
// "Animals:" ["cat", "dog"] "&" ["cat", "dog"]

console.log('Fruit:', fruit_filtered, '&', fruit);
//"Fruit:" ["apple", "orange"] "&" ["apple", "orange"]