Create a function that given an array of dates returns the average date in string form.

Examples

averageDate([]) ➞ null

averageDate([
  new Date(Date.UTC(1970, 0, 1))
]) ➞ "1970-01-01T00:00:00.000Z"

averageDate([
  new Date(Date.UTC(1970, 0, 1)),
  new Date(Date.UTC(1971, 0, 1))
]) ➞ "1970-07-02T12:00:00.000Z"

Notes

• For the return value you can use the .toISOString() method.
• If dates is an empty array return null.