iterables-code-10.js

const data = {
 items: ["A", "B", "C"],
 pointerIndex: 0,
 [Symbol.iterator]: function () {
   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 };
 }
}


const it = data[Symbol.iterator];

console.log(it()) //o: {value: "A", done: false}
console.log(it()) //o: {value: "B", done: false}
console.log(it()) //o: {value: "C", done: false}
console.log(it()) //o: {value: undefined, done: true}