const myObject = {
  a: 1,
  b: 2,
  c: 3,
  [Symbol.iterator]: function* () {
    for (let key of Object.keys(this)) {
      yield this[key];
    }
  }
};

const iter = myObject[Symbol.iterator]();
console.log(iter.next().value);
console.log(iter.next().value);
console.log(iter.next().value);