The Iterator pattern provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

class Iterator {
  constructor(items) {
    this.items = items;
    this.index = 0;
  }

  next() {
    return this.items[this.index++];
  }

  hasNext() {
    return this.index < this.items.length;
  }
}

class IterableCollection {
  constructor(items) {
    this.items = items;
  }

  createIterator() {
    return new Iterator(this.items);
  }
}

1. Iterator Class

   • Constructor: Initializes the items array and sets the starting index to 0.
   • next() Method: Returns the current item and increments the index.
   • hasNext() Method: Checks if there are more items to iterate over.

2. IterableCollection Class

   • Constructor: Initializes the items array.
   • createIterator() Method: Creates and returns a new Iterator instance for the collection.

// Usage
const collection = new IterableCollection(["item1", "item2", "item3"]);
const iterator = collection.createIterator();

while (iterator.hasNext()) {
  console.log(iterator.next());
}

• Creating Collection: An instance of IterableCollection is created with an array of items.
• Creating Iterator: An iterator is created for the collection using createIterator().
• Iterating: A while loop is used to iterate over the collection, printing each item until there are no more items.

This code defines an Iterator class to traverse a collection and an IterableCollection class to create an iterator for its items.