How to declare Hash.new(0) with 0 default value for counting objects in JavaScript?

Question

I\'m trying to iterate through an array of digits and count how many times each digit is found in the array.

In ruby it\'s easy, I just declare a Hash.new(0)

Answer 1

In Javascript you do it with Array.reduce

const reducer = (acc, e) => acc.set(e, (acc.get(e) || 0) + 1);
[1, 0, 0, 0, 1, 0, 0, 1].reduce(reducer, new Map())
//⇒ Map(2) {1 => 3, 0 => 5}