iterables-code-12.js

const data = {
 items: ["A", "B", "C"],
 pointerIndex: 0,
 next() {
   if (this.pointerIndex < this.items.length) // if done
     return { value: this.items[this.pointerIndex++], done: false }
   else // if not done
     return { value: undefined, done: true };
 },
  [Symbol.iterator]: function() {
   this.pointerIndex = 0;
   return { next: this.next.bind(this) }
 }
}

for (let item of data) {
  console.log(item)
} //o: A B C