exercise.js

let hogwarts = [
  {
    firstName: "Harry",
    lastName: "Potter",
    house: "Gryffindor",
    pet: "Owl",
    occupation: "Student",
  },
  {
    firstName: "Ron",
    lastName: "Weasley",
    house: "Gryffindor",
    pet: "Scabbers",
    occupation: "Student",
  },
  {
    firstName: "Hermione",
    lastName: "Granger",
    house: "Gryffindor",
    pet: "Cat",
    occupation: "Student",
  },
  {
    firstName: "Draco",
    lastName: "Malfoy",
    house: "Slytherin",
    pet: null,
    occupation: "Student",
  },
  {
    firstName: "Cedric",
    lastName: "Diggory",
    house: "HufflePuff",
    pet: null,
    occupation: "Student",
  },
  {
    firstName: "Severus",
    lastName: "Snape",
    house: "Slytherin",
    pet: null,
    occupation: "Teacher",
  },
  {
    firstName: "Filius",
    lastName: "Flitwick",
    house: "Ravenclaw",
    pet: null,
    occupation: "Teacher",
  },
  {
    firstName: "Pomona",
    lastName: "Sprout",
    house: "Hufflepuff",
    pet: null,
    occupation: "Teacher",
  },
  {
    firstName: "Minerva",
    lastName: "McGonagall",
    house: "Gryffindor",
    pet: null,
    occupation: "Teacher",
  },
  {
    firstName: "Albus",
    lastName: "Dumbledore",
    house: "Gryffindor",
    pet: "Phoenix",
    occupation: "Teacher",
  },
];

let { firstName, lastName, house, pet} = hogwarts;

function property(array){
  let gryfindorHouse = array.filter(hogwarts => hogwarts.house === "Gryffindor")    //filter mean to give only the elements that pass a certain condition specified by a provided function
  let getAllName = gryfindorHouse.map( hogwarts =>`${hogwarts.firstName}${hogwarts.lastName}`);
  return getAllName;
}
console.log(property(hogwarts));

function whoHavePet(array){
  let findPet = array.filter(hogwarts => hogwarts.pet !== null)
  let getPet = findPet.map( hogwarts =>`${hogwarts.firstName}${hogwarts.lastName}`);
  return getPet;
}

console.log(whoHavePet(hogwarts));