Given a string of parenthesis, return the number of parenthesis you need to add to the string in order for it to be balanced.

numBalanced.ts

const numBalanced = (str: string) => {
  const { open, closed } = str.split('').reduce(({ open, closed }, s) => ({ open: open + (s === '(' ? 1 : 0), closed: closed + (s === ')' ? 1 : 0) }), { open: 0, closed: 0 })
  return Math.abs(open - closed)
}