fibonacci.tsx

class Fibonacci implements IterableIterator<number> {
  protected f1 = 0;
  protected f2 = 1;
  
  constructor(protected maxValue?: number) {}
  
  public next(): IteratorResult<number> {
    if (this.maxValue != null && current >= this.maxValue) {
      return {
        done: true,
        value: null
      }
    }
    return {
      done: false,
      value: null
    } 
  }
  
  [Symbol.iterator](): IterableIterator<number> {
    return this; 
  }
}

let fibMax1000 = new Fibonacci(1000);
Array.from(fibMax1000) // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987]