sum() : The sum() method returns the sum of all items in the collection :
collect([1, 2, 3]).sum();
// 6
If the collection contains nested arrays or objects, you should pass a key to use for determining which values to sum :
const collection = collect([
{ name: 'My story', pages: 176 },
{ name: 'Fantastic Beasts and Where to Find Them', pages: 1096 },
]);
collection.sum('pages');
// 1272
In addition, you may pass your own callback to determine which values of the collection to sum :
const collection = collect([
{ name: 'Desk', colors: ['Black', 'Mahogany'] },
{ name: 'Chair', colors: ['Black'] },
{ name: 'Bookcase', colors: ['Red', 'Beige', 'Brown'] },
]);
const total = collection.sum(product => product.colors.length);
// 6
