group_objects_with_reduce.js

function groupBy(arr, func){
  return arr
    .reduce((acc, item) => {
       const key = func(item);
       if (!acc[key]) {
         acc[key] = [];
       }
       acc[key].push(item);
       return acc;
    }, Object.create(null));
}

const basket = [
  { name:"apple", type: "fruit" }, 
  { name:"broccoli", type: "vegetable" },
  { name:"banana", type: "fruit" }
];

const grouped = groupBy(basket, food => food.type);
console.log(grouped); 
/*
Outputs:
{ 
  fruit: [
            {name: "apple", type: "fruit"}, 
            {name: "banana", type: "fruit"}
         ],
  vegetable: [{ name:"broccoli", type: "vegetable" }]
}
*/