wrapper to add .next() and .prev() and current() to array, without prototype

iterifyArray.js

const iterifyArr = function(arr) {
  var cur = 0;
  arr.next = function() {
    if (++cur <= this.length - 1) {
      return this[cur];
    } else {
      cur = 0;
      return this[cur];
    }
  };
  arr.prev = function() {
    if (--cur < 0) {
      cur = this.length - 1;
      return this[cur];
    } else {
      return this[cur];
    }
  };
  arr.current = function() {
    return this[cur];
  };
  return arr;
};

module.exports = iterifyArr;