[JS] CroCoder / 코딩테스트 입문 / 제품별 평균

---

문제

Map, Filter, Reduce - Code Exercises | CroCoder

---

메모

// 배열 속 객체 요소의 합

const objects = [{ x: 1 }, { x: 2 }, { x: 3 }];
const sum = objects.reduce((acc, cur) => acc + cur.x, 0); // 초기값 0 필수

console.log(sum); // 6

---

정답

const products = [
  { name: "Product 1", price: 20, category: "Electronics" },
  { name: "Product 2", price: 30, category: "Clothes" },
  { name: "Product 3", price: 40, category: "Electronics" },
  { name: "Product 4", price: 50, category: "Clothes" },
  { name: "Product 5", price: 60, category: "Clothes" },
  { name: "Product 6", price: 70, category: "Electronics" },
  { name: "Product 7", price: 80, category: "Clothes" },
  { name: "Product 8", price: 90, category: "Electronics" },
];

const productsByCategory = products.reduce((acc, cur) => {
  if (acc[cur.category] === undefined) {
    acc[cur.category] = [];
  }
  acc[cur.category].push(cur);
  return acc;
}, {});

const avgPriceByCategory = Object.keys(productsByCategory).map(x => {
  const sum = productsByCategory[x].reduce((acc, cur) => acc + cur.price, 0);
  return { category: x, average: sum / productsByCategory[x].length };
});

console.log(avgPriceByCategory);

---