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

You can use Map,

• initialize hash as Map
• Loop through array, if key is already present in hash increase it's value by 1 else set it to 1

let arr = [1, 0, 0, 0, 1, 0, 0, 1]
let hash = new Map()

arr.forEach(val => {
  hash.set(val, (hash.get(val) || 0) + 1)
})

console.log([...hash])