Recursive function to get sum of items in an array, written in JavaScript

recursiveArraySum.js

function arraySum(arr){
  if (arr.length < 1){
    return 0
  } else if (arr[0].constructor === Array){
    return arraySum(arr[0]) + arraySum(arr.slice(1))
  } else {
    return arr[0] + arraySum(arr.slice(1))
  }
}