3-class.js

'use strict';

class Counter {
  constructor(begin, end, step = 1) {
    this.begin = begin;
    this.end = end;
    this.step = step;
  }
  [Symbol.iterator]() {
    const end = this.end;
    let i = this.begin;
    const step = this.step;
    const iterator = {
      next() {
        const item = {
          value: i,
          done: i > end
        };
        i += step;
        return item;
      }
    };
    return iterator;
  }
}

// Usage

const iterable = new Counter(0, 3);

const iterator = iterable[Symbol.iterator]();
const step1 = iterator.next();
const step2 = iterator.next();
const step3 = iterator.next();
const step4 = iterator.next();
console.log({ step1, step2, step3, step4 });

for (const step of iterable) {
  console.log({ step });
}

console.log({ steps: [...iterable] });