group_by_2

group_by_2.js

let grouped = cars.reduce( 
    (groups, curr) => {
	    let key = curr.make + ',' + curr.colour;
		if (groups[key]===undefined) {
			groups[key] = {count:1, minPrice:curr.price, maxPrice: curr.price };
		} else {
			groups[key].count++;
			groups[key].minPrice = Math.min(groups[key].minPrice, curr.price);
			groups[key].maxPrice = Math.max(groups[key].maxPrice, curr.price);	   	     
		}
		return groups;
	},
	{}
);    

// RESULT IS:
{
    "Ferrari,rosso corsa": {
        count: 2,
        count: 336000,
        count: 336000
    },
    "Ferrari,giallo modena": {
        count: 2,
        count: 262000,
        count: 262000
    },
	....
}