JavaScript中如何实现堆？

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

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

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

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

  // 交换两个节点
  swap(index1, index2) {
    const temp = this.heap[index1];
    this.heap[index1] = this.heap[index2];
    this.heap[index2] = temp;
  }

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

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

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

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

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

  // 插入一个新元素
  insert(value) {
    this.heap.push(value);
    this.siftUp(this.heap.length - 1);
  }

  // 删除并返回最小元素
  extractMin() {
    if (this.heap.length === 0) {
      return null;
    }
    if (this.heap.length === 1) {
      return this.heap.pop();
    }

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

    return min;
  }

  // 获取最小元素但不删除
  peek() {
    return this.heap[0];
  }

  // 获取堆的大小
  size() {
    return this.heap.length;
  }

  // 检查堆是否为空
  isEmpty() {
    return this.heap.length === 0;
  }
}