priorityQueue.js

class PriorityQueue {
  constructor(){
      this.values = [];
  }
  enqueue(val, priority){
      let newNode = new Node(val, priority);
      this.values.push(newNode);
      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.priority >= parent.priority) break;
          this.values[parentIdx] = element;
          this.values[idx] = parent;
          idx = parentIdx;
      }
  }
  dequeue(){
      const min = this.values[0];
      const end = this.values.pop();
      if(this.values.length > 0){
          this.values[0] = end;
          this.sinkDown();
      }
      return min;
  }
  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.priority < element.priority) {
                  swap = leftChildIdx;
              }
          }
          if(rightChildIdx < length){
              rightChild = this.values[rightChildIdx];
              if(
                  (swap === null && rightChild.priority < element.priority) || 
                  (swap !== null && rightChild.priority < leftChild.priority)
              ) {
                 swap = rightChildIdx;
              }
          }
          if(swap === null) break;
          this.values[idx] = this.values[swap];
          this.values[swap] = element;
          idx = swap;
      }
  }
}

class Node {
  constructor(val, priority){
      this.val = val;
      this.priority = priority;
  }
}

let ER = new PriorityQueue();