batches.ts

export class Batches<T> implements Iterable<T[]> {
  constructor(private values: T[], private size: number) {
  }

  [Symbol.iterator](): Iterator<T[]> {
    return new BatchesIterator(this.values, this.size);
  }
}

class BatchesIterator<T> implements Iterator<T[]> {
  private done = false;
  private index = 0;

  constructor(private values: T[], private size: number) {
  }

  next(): IteratorResult<T[], number | undefined> {
    if (this.done) {
      return {
        done: this.done,
        value: undefined
      }
    }
    if (this.index >= this.values.length) {
      this.done = true;
      return {
        done: this.done,
        value: this.index
      }
    }
    const value = this.values.slice(this.index, this.index + this.size);
    this.index += this.size;
    return {
      done: false,
      value
    }
  }
}