Min-Heap in JavaScript

const swap = require('../swap');

function Heap(){
  this.heap = [];
}

Heap.prototype.getParent = function(index){
  return (index-1)/2;
}

Heap.prototype.getLeft = function(index){
  return (2*index)+1;
}

Heap.prototype.getRight = function(index){
  return (2*index)+2;
}

//inserts a new value to the min-heap
Heap.prototype.insert = function(value){
  this.heap.push(value);
  this.heapifyUp(this.heap.length-1);
  return;
}

//deletes any node at given index
Heap.prototype.delete = function(index){
  if(index === 0){
    this.heap[0] = this.heap[this.heap.length-1];
    this.heap.splice(this.heap.length-1, 1);
    this.heapifyDown(0);
    return;
  }

  this.heap[index] = this.heap[this.heap.length-1];
  this.heap.splice(this.heap.length-1, 1);
  var parent = this.getParent(index);
  (this.heap[index]<this.heap[parent])? this.heapifyUp(index) : this.heapifyDown(index);
  return;
}

//extracts min value and recalibrates minheap
Heap.prototype.extractMin = function(){
  var temp = this.heap[0];

  swap(this.heap, 0, (this.heap.length-1));
  this.heap.slice((this.heap.length-1), 1);
  this.heapifyDown(0);

  return temp;
}

//decreases the value of node at given index by given value
Heap.prototype.decrease = function(index, value){

  if((this.heap[index]-value)<0) return false;

  this.heap[index] = this.heap[index]-value;
  (index === 0) ? this.heapifyDown(0) : this.heapifyUp(index);
  return;
}


Heap.prototype.heapifyUp = function(index){

  var parent = this.getParent(index);

  while(parent>=0 && this.heap[parent]>this.heap[index]){
    swap(this.heap, parent, index);
    index = parent;
    parent = this.getParent(index);
  }

}

Heap.prototype.heapifyDown = function(index){

  var left = this.getLeft(index);
  var right = this.getRight(index);

  while(this.heap[index]>this.heap[left] || this.heap[index]>this.heap[right]){
    if(this.heap[index]>this.heap[left]){
      swap(this.heap, left, index);
      index = left;
      left = this.getLeft(index);
    }
    if(this.heap[index]>this.heap[right]){
      swap(this.heap, right, index);
      index = right;
      right = this.getLeft(index);
    }
  }

}