add a key and an array in a from group code example
Example 1: javascript group by key
var cars = [{ make: 'audi', model: 'r8', year: '2012' }, { make: 'audi', model: 'rs5', year: '2013' }, { make: 'ford', model: 'mustang', year: '2012' }, { make: 'ford', model: 'fusion', year: '2015' }, { make: 'kia', model: 'optima', year: '2012' }],
result = cars.reduce(function (r, a) {
r[a.make] = r[a.make] || [];
r[a.make].push(a);
return r;
}, Object.create(null));
console.log(result);
Example 2: javascript group by sum array reduce
var array = [
{ Id: "001", qty: 1 },
{ Id: "002", qty: 2 },
{ Id: "001", qty: 2 },
{ Id: "003", qty: 4 }
];
var result = [];
array.reduce(function(res, value) {
if (!res[value.Id]) {
res[value.Id] = { Id: value.Id, qty: 0 };
result.push(res[value.Id])
}
res[value.Id].qty += value.qty;
return res;
}, {});
console.log(result)