array-grouping.js

const products = [
  { name: 'apples', category: 'fruits', count: 1 },
  { name: 'oranges', category: 'fruits', count: 2 },
  { name: 'potatoes', category: 'vegetables', count: 1 },
  { name: 'kettle chips', category: 'snacks', count: 3 },
];
const groupByCategory = products.reduce((group, product) => {
  const { category } = product;
  group[category] = group[category] ?? [];
  group[category].push(product);
  return group;
}, {});


const groupBy = (arr, key) => arr.reduce((group, item) => {
  group[item[key]] = group[item[key]] ?? [];
  group[item[key]].push(item)
  return group
}, {})
console.log(groupByCategory);
console.log(groupBy(products, 'count'));