How to move to prev/next element of an array with JavaScript?

To move to prev/next element of an array with JavaScript, we can define our own array class.

For instance, we write

class TraversableArray extends Array {
  next() {
    return this[++this.current];
  }
}

to define the TraversableArray class that extends the Array class.

In it, we add the next method that returns the object at the current index after incrementing it by 1.