Heap class with customizable comparator

heap.js

class Heap {
  constructor(comparator = (a, b) => a - b) {
    this.heap = []
    this.comparator = comparator
  }

  getParentIndex(index) {
    return Math.floor((index - 1) / 2)
  }

  getLeftChildIndex(index) {
    return 2 * index + 1
  }

  getRightChildIndex(index) {
    return 2 * index + 2
  }

  add(val) {
    this.heap.push(val)
    this.bubbleUp(this.heap.length - 1)
    return this
  }

  bubbleUp(index) {
    let currentIndex = index
    let parentIndex = this.getParentIndex(currentIndex)

    // Keep bubbling up while parent should be below current
    while (parentIndex >= 0 && this.comparator(this.heap[parentIndex], this.heap[currentIndex]) > 0) {
      // Swap
      const temp = this.heap[currentIndex]
      this.heap[currentIndex] = this.heap[parentIndex]
      this.heap[parentIndex] = temp

      currentIndex = parentIndex
      parentIndex = this.getParentIndex(currentIndex)
    }
  }

  remove() {
    if (this.heap.length === 0) return null
    if (this.heap.length === 1) return this.heap.pop()

    const result = this.heap[0]
    this.heap[0] = this.heap.pop()
    this.bubbleDown(0)

    return result
  }

  bubbleDown(index) {
    let currentIndex = index

    while (true) {
      const leftChildIndex = this.getLeftChildIndex(currentIndex)
      const rightChildIndex = this.getRightChildIndex(currentIndex)
      let candidateIndex = currentIndex

      // Find which child should be the parent (if any)
      if (leftChildIndex < this.heap.length && 
          this.comparator(this.heap[candidateIndex], this.heap[leftChildIndex]) > 0) {
        candidateIndex = leftChildIndex
      }

      if (rightChildIndex < this.heap.length && 
          this.comparator(this.heap[candidateIndex], this.heap[rightChildIndex]) > 0) {
        candidateIndex = rightChildIndex
      }

      if (candidateIndex === currentIndex) break

      // Swap
      const temp = this.heap[currentIndex]
      this.heap[currentIndex] = this.heap[candidateIndex]
      this.heap[candidateIndex] = temp

      currentIndex = candidateIndex
    }
  }

  peek() {
    return this.heap[0]
  }

  get size() {
    return this.heap.length
  }
}