Take the average number of a x list of numbers in a sequence

average.js

export default function average (limit) {
  let list = []
  let current = 0

  return (x) => {
    list = [...list, x]

    if (list.length < limit) return current

    current = list.reduce((acc, x, index) => {
      if (index === limit - 1) {
        return acc / limit
      }

      return acc + x
    }, 0)

    list = []

    return current
  }
}