How to count items in a nested array?

Question

I have the following array in my Angular application:

Each element contains a supplier and one or more products.

How can I get a count of all the products that are returned?

I can get the products themselves by doing this:

array.map(x=>x.products)

And I can get a count of the products for each element by doing this:

array.map(x=>x.products.length)

But how do I then sum that?

Answer 1

You can use reduce to handle this.

const totalProducts = arr.reduce((count, current) => count + current.products.length, 0);

The concept of reduce is to take an array and "reduce" it down to a single entity. That entity can be an object, another array, number...

The 0 at the end initializes the reduce entity. Since you are going for a sum, set it to 0 and then add to it.