Directions:

Implement a peek() method in this Queue class. Peek should return the last element (the next one to be returned) from the queue without removing it.
Implement the weave(q1, q2) function.
- Weave receives two queues as arguments and combines the contents of each into new, third queue.
- The third queue should contain the alternating content of the two queues.
- The function should handle queues of different lengths without inserting 'undefined' into the new one.
- Do not access the array inside of any queue, only use the enqueue, dequeue, and peek functions.

Example:

const queueOne = new Queue()
queueOne.enqueue(1)
queueOne.enqueue(2)
const queueTwo = new Queue()
queueTwo.enqueue('Hi')
queueTwo.enqueue('There')

const q = weave(queueOne, queueTwo)
q.dequeue() // 1
q.dequeue() // 'Hi'
q.dequeue() // 2
q.dequeue() // 'There'

Weave Solution

class Queue {
  constructor() {
    this.data = []
  }

  enqueue(item) {
    this.data.push(item)
  }

  dequeue(item) {
    return this.data.shift()
  }

  peek(item) {
    return this.data[0]
  }

  isEmpty() {
    return this.data.length === 0
  }
}

function weave(sourceOne, sourceTwo) {
  const q = new Queue()

  // as long as our next element is NOT undefined...
  while (sourceOne.peek() || sourceTwo.peek()) {
    if (sourceOne.peek()) {
      q.enqueue(sourceOne.dequeue())
    }
    if (sourceTwo.peek()) {
      q.enqueue(sourceTwo.dequeue())
    }
  }
  return q
}

Create a new Queue object with new Queue().
Iterate through each input queue, dequeueing each element and adding it to the new queue. This will shorten the input queues.
If one queue is empty, add the remaining elements from the other queue to the new queue.