queue data structure, javascript

priorityQueue.js

function createPriorityQueue() {
  const highPriorityQueue = createQueue()
  const lowPriorityQueue = createQueue()
  
  return {
    enqueue(item, isHighPriority = false) {
      (isHighPriority
        ? highPriorityQueue
        : lowPriorityQueue
      ).enqueue(item)
    },
    
    dequeue() {
      return (!highPriorityQueue.isEmpty()
        ? highPriorityQueue
        : lowPriorityQueue
      ).dequeue()
    },
    
    peek() {
      return (!highPriorityQueue.isEmpty()
        ? highPriorityQueue
        : lowPriorityQueue
      ).peek()
    },
    
    get length() {
      return (
        highPriorityQueue.length + lowPriorityQueue.length
      )
    },
    
    isEmpty() {
      return (
        highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty()
      )
    }
  }
}

queue.js

function createQueue() {
  const queue = []

  return {
    enqueue(item) {
      queue.unshift(item)
    },
    
    dequeue() {
      return queue.pop()
    },
    
    peek() {
      return queue[queue.length - 1]
    },
    
    get length() {
      return queue.length
    },
    
    isEmpty() {
      return queue.length === 0
    }
  }
}