Using reduce to group an array of products by category

products-reducer.js

const products = [
  {
    name: 'Disposable Mask',
    price: 8.75,
    category: 'Health'
  },
  {
    name: 'Painkiller',
    price: 2.35,
    category: 'Health'
  },
  {
    name: 'White Chair',
    price: 24.50,
    category: 'Furniture'
  }
];

const productCategoryGrouper = ( productsByCategory, product ) => ({
  ...productsByCategory,
  [product.category]: [
    ...(productsByCategory[product.category] || []),
    product
  ]
});

const productsByCategory = products.reduce(productCategoryGrouper, {});

/**
  productsByCategory:
    {
      Health: [
        {
          name: 'Disposable Mask',
          price: 8.75,
          category: 'Health'
        },
        {
          name: 'Painkiller',
          price: 2.35,
          category: 'Health'
        }
      ],
      Furniture: [
        {
          name: 'White Chair',
          price: 24.50,
          category: 'Furniture'
        }
      ]
    }
**/