heap.js

class MaxBinaryHeap {
  constructor(){
      this.values = [];
  }
  insert(element){
      this.values.push(element);
      this.bubbleUp();
  }
  bubbleUp(){
      let idx = this.values.length - 1;
      const element = this.values[idx];
      while(idx > 0){
          let parentIdx = Math.floor((idx - 1)/2);
          let parent = this.values[parentIdx];
          if(element <= parent) break;
          this.values[parentIdx] = element;
          this.values[idx] = parent;
          idx = parentIdx;
      }
  }
  extractMax(){
      const max = this.values[0];
      const end = this.values.pop();
      if(this.values.length > 0){
          this.values[0] = end;
          this.sinkDown();
      }
      return max;
  }
  sinkDown(){
      let idx = 0;
      const length = this.values.length;
      const element = this.values[0];
      while(true){
          let leftChildIdx = 2 * idx + 1;
          let rightChildIdx = 2 * idx + 2;
          let leftChild,rightChild;
          let swap = null;

          if(leftChildIdx < length){
              leftChild = this.values[leftChildIdx];
              if(leftChild > element) {
                  swap = leftChildIdx;
              }
          }
          if(rightChildIdx < length){
              rightChild = this.values[rightChildIdx];
              if(
                  (swap === null && rightChild > element) || 
                  (swap !== null && rightChild > leftChild)
               ) {
                  swap = rightChildIdx;
              }
          }
          if (swap === null) break;
          this.values[idx] = this.values[swap];
          this.values[swap] = element;
          idx = swap;
      }
  }
}

let heap = new MaxBinaryHeap();
heap.insert(41);
heap.insert(39);
heap.insert(33);
heap.insert(18);
heap.insert(27);
heap.insert(12);
heap.insert(55);