jmporchet

const obj = {
  sub: {
    array: []
  },
  [Symbol.iterator]() {
    let index = 0;
    return {
      next: () => {
        // you could insert custom logic here, like stepping 3 by 3, filtering, etc.
        if ( index >= this.sub.array.length ) return { done: true }

jmporchet

const obj = {
  sub: {
    array: [1,2,3,4,5,6,7,8,9]
  },
  *[Symbol.iterator]() {
    for (let i = 0; i < this.sub.length; i++) {
      yield this.sub[i];
    }
  }
}