Definition

Queues are a data type or collection in which the collection maintains a particular oder in which the elements are added and removed. Queues follow First-In-First-Out (FIFO) principle. The first element added to the queue is the first one to be removed.

Implementation

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
  }
}

// Test
const queue = new Queue()

queue.isEmpty() // true

queue.enqueue('A')
queue.enqueue('B')
queue.enqueue('C')
queue.enqueue('D')
queue.enqueue('E')

queue.isEmpty() // false

queue.peek() // 'A'

queue.dequeue() // 'A'
queue.dequeue() // 'B'
queue.dequeue() // 'C'

• Create a class with a constructor that initializes an empty array of data.
• Define an enqueue() method to add an element to the end of the data array.
• Define a dequeue() method to remove an element from the start of the data array.
• Define a peek() method, which retrieves the value of the first element in the data array, without removing it.
• Define an isEmpty() method to determine if the data array is empty.