Queue

function createLinkedListQueue() {
  let length = 0
  let head = undefined
  let tail = undefined
  return {
    enqueue(value) {
      enqueueNode(value)
    },
    dequeue() {
      return dequeueNode()
    },
    size() {
      return length
    },
    head() {
      return head
    },
    tail() {
      return tail
    }
  }
  function enqueueNode(value) {
    const node = {
      value,
      next: undefined 
    }
    if(!head) {
      head = node
      tail = node
    }
    else {
      tail.next = node
      tail = node
    }
    length += 1 
  }
  function dequeueNode() {
    if(head) {
      const value = head.value
      head = head.next
      length -= 1
      return value
    }
    tail = undefined
    return undefined
  }
}

function createSingleArrayQueue() {
  let queue = []
  return {
    enqueue(element) {
      queue.push(element)
    },
    dequeue() {
      return queue.shift()
    },
    size() {
      return queue.length
    }
  }
}

function createDoubleArrayQueue() {
  let input = []
  let output = []
  return {
    enqueue(element) {
      input.push(element)
    },
    dequeue() {
      if(output.length === 0) {
        pivot()
      }
      return output.pop()
    },
    size() {
      return (input.length + output.length)
    }
  }
  function pivot() {
    output = input.reverse()
    input = []
  }
}

const singleQ = createSingleArrayQueue()
const doubleQ = createDoubleArrayQueue()
const linkedListQ = createLinkedListQueue()
const queueSize = 10000
console.log(`Queue size: ${queueSize}`)

for(let i = 0; i < queueSize; i++) {
  singleQ.enqueue('testString' + i)
  doubleQ.enqueue('testString' + i)
  linkedListQ.enqueue('testString' + i)
}

const LINKED_LIST = 'Linked List Queue'
const DOUBLE_ARRAY = 'Double Array Queue'
const SINGLE_ARRAY = 'Single Array Queue'

console.time(LINKED_LIST)
for(let i = 0; i < queueSize; i++) {
  linkedListQ.dequeue()
}
console.timeEnd(LINKED_LIST)

console.time(DOUBLE_ARRAY)
for(let i = 0; i < queueSize; i++) {
  doubleQ.dequeue()
}
console.timeEnd(DOUBLE_ARRAY)

console.time(SINGLE_ARRAY)
for(let i = 0; i < queueSize; i++) {
  singleQ.dequeue()
}
console.timeEnd(SINGLE_ARRAY)