Method peek

stacks/queue-via-stacks.js:30–33

()

    return this.stackOldest.pop();
  }
  peek() {
    this.#shiftStacks(); // Ensure stackOldest has the current elements
    return this.stackOldest.peek();
  }
  empty() {
    return this.stackNewest.size() + this.stackOldest.size() === 0;
  }