如何用JavaScript实现优先队列？

class PriorityQueue {
  constructor() {
    this.heap = [];
  }

  // 交换两个节点的位置
  swap(i, j) {
    const temp = this.heap[i];
    this.heap[i] = this.heap[j];
    this.heap[j] = temp;
  }

  // 获取父节点的索引
  parentIndex(i) {
    return Math.floor((i - 1) / 2);
  }

  // 获取左孩子节点的索引
  leftChildIndex(i) {
    return 2 * i + 1;
  }

  // 获取右孩子节点的索引
  rightChildIndex(i) {
    return 2 * i + 2;
  }

  // 向上调整堆
  siftUp(index) {
    let parent = this.parentIndex(index);
    while (index > 0 && this.heap[parent].priority > this.heap[index].priority) {
      this.swap(parent, index);
      index = parent;
      parent = this.parentIndex(index);
    }
  }

  // 向下调整堆
  siftDown(index) {
    let minIndex = index;
    const leftIndex = this.leftChildIndex(index);
    const rightIndex = this.rightChildIndex(index);

    if (leftIndex < this.heap.length && this.heap[leftIndex].priority < this.heap[minIndex].priority) {
      minIndex = leftIndex;
    }

    if (rightIndex < this.heap.length && this.heap[rightIndex].priority < this.heap[minIndex].priority) {
      minIndex = rightIndex;
    }

    if (index !== minIndex) {
      this.swap(index, minIndex);
      this.siftDown(minIndex);
    }
  }

  // 插入一个新元素
  enqueue(element, priority) {
    this.heap.push({ element, priority });
    this.siftUp(this.heap.length - 1);
  }

  // 删除并返回优先级最高的元素
  dequeue() {
    if (this.heap.length === 0) return null;
    if (this.heap.length === 1) return this.heap.pop().element;

    const min = this.heap[0].element;
    this.heap[0] = this.heap.pop();
    this.siftDown(0);

    return min;
  }

  // 查看优先级最高的元素
  peek() {
    return this.heap.length > 0 ? this.heap[0].element : null;
  }

  // 检查队列是否为空
  isEmpty() {
    return this.heap.length === 0;
  }
}

const pq = new PriorityQueue();
pq.enqueue('Task 1', 3);
pq.enqueue('Task 2', 1);
pq.enqueue('Task 3', 2);

console.log(pq.dequeue()); // 输出: Task 2
console.log(pq.dequeue()); // 输出: Task 3
console.log(pq.dequeue()); // 输出: Task 1