group-by.js

const array = [
  { id: 1, category: 'Apple' },
  { id: 1, category: 'Orange' },
  { id: 3, category: 'Orange' },
  { id: 4, category: 'Grape' },
  { id: 5, category: 'Grape' },
]

function groupBy(array, key) {
  const keys = (array, key) => array.reduce((acc, item) => acc.add(item[key]), new Set());
  return Array
    .from(keys(array, key))
    .map(k => array.filter(x => x[key] === k))
}

console.log(groupBy(array, 'id'))

function group(array, key) {
  const withKeys = array.reduce((acc, item) => {
    acc[key] = acc[key] || [];
    acc[key].push(item);
    return acc;
  }, {})
  return Object.values(withKeys);
}

console.log(group(array, 'id'));