JS (ES6): Filter array based on nested array attributes

Question

I have an array, which looks like this:

const persons = [
  {
    name: \"Joe\",
    animals: [
      {species: \"dog\", name: \"Bolt\"},
      {species: \"c         


        

Answer 1

You havent checked against the length of the second filter.

Filer only includes results that return a true value. So we need to provide the second filter with a way of returning true if it finds something. We can do that by saying, if the returned array is > 0

const persons = [
  {
    name: "Joe",
    animals: [
      {species: "dog", name: "Bolt"},
      {species: "cat", name: "Billy"},
    ]
  },
  {
    name: "Bob",
    animals: [
      {species: "dog", name: "Snoopy"}
    ]
  }
];

const filtered = persons.filter(p => p.animals.filter(a => a.species === "cat").length > 0)

console.log(filtered)