Simple queue and Stack in js

queue.js

function createStack() {
  let head = null
  let length = 0
  return {
    push: (data) => {
      head = { data, next: head }
      length++
    },
    pop: () => {
      if (head === null) return null
      let oldHead = head
      head = head.next
      length--
      return oldHead.data
    },
    length: () => length,
  }
}

function createQueue() {
  const stack1 = createStack()
  const stack2 = createStack()
  return {
    enqueue: (data) => stack1.push(data),
    dequeue: () => {
      if (!stack2.length() && stack1.length()) {
        while (stack1.length()) stack2.push(stack1.pop())
      }
      return stack2.pop()
    },
  }
}

const queue = createQueue()
queue.enqueue(1)
console.log("enqueued value: 1")
queue.enqueue(2)
console.log("enqueued value: 2")
queue.enqueue(3)
console.log("enqueued value: 3")
console.log("dequed: value: " + queue.dequeue())
console.log("dequed: value: " + queue.dequeue())
queue.enqueue(4)
console.log("enqueued value: 4")
queue.enqueue(5)
console.log("enqueued value: 5")
console.log("dequed: value: " + queue.dequeue())
console.log("dequed: value: " + queue.dequeue())
console.log("dequed: value: " + queue.dequeue())
console.log("dequed: value: " + queue.dequeue())