Priority Queue for Node.js

A Priority Queue implementation that maintains a sorted queue of items. Use a custom comparator function to compare items in the queue. If a custom comparator is not passed to the PriorityQueue's constructor, a default comparator will be used. Based on the comparator used, the queue can store items in ascending or descending order.

Installation

NPM:

npm install priority-queue-node

Github Packages: (Note: Ensure your registry url is pointed at https://npm.pkg.github.com)

npm install @vincegando/priority-queue-node

• API
  • constructor([comparator: Function)]
  • enqueue(item: any)
  • dequeue(): any
  • peek(): any
  • size(): Number
  • isEmpty(): Boolean

API

constructor([comparator: Function])

Initialize the Priority Queue.

Arguments

• (optional) comparator (Function) - The compare function used to order items in the queue

To use the default comparator, pass no arguments to the constructor.

const PriorityQueue = require('priority-queue-node')

const priorityQueue = new PriorityQueue()

To use a custom comparator, pass a compare function as the only argument to the constructor.

const PriorityQueue = require('priority-queue-node')

const customQueue = new PriorityQueue((a, b) => {
  return b - a
})

enqueue(item: any)

Add an item to the PriorityQueue.

Arguments

• item (any) - The item to add to the queue

NOTE: If undefined or null is passed as the item argument, nothing will be added to the queue.

// Add a number
priorityQueue.enqueue(5)

// Add a string
priorityQueue.enqueue('foo')

// Add an object
priorityQueue.enqueue({ bar: 'baz' })

dequeue(): any

Remove and return the item from the beginning of the PriorityQueue.

returns any: The item at the beginning of the queue

// Starting queue: [1, 3, 5], comparator: default

const item1 = priorityQueue.dequeue() // 1
const item2 = priorityQueue.dequeue() // 3
const item3 = priorityQueue.dequeue() // 5

peek(): any

Return the item from the beginning of the PriorityQueue.

returns any: The item at the beginning of the queue

// Starting queue: [1, 3, 5], comparator: default

const item1 = priorityQueue.peek() // 1
const item2 = priorityQueue.peek() // 1
const item3 = priorityQueue.peek() // 1

size(): Number

Return the current size of the PriorityQueue.

returns Number: The current size of the queue

priorityQueue.enqueue(1)
priorityQueue.enqueue(2)
priorityQueue.enqueue(3)

const size = priorityQueue.size() // 3

isEmpty(): Boolean

Return true if the PriorityQueue is empty, false if not.

returns Boolean: true if the queue is empty, false if not

const empty1 = priorityQueue.isEmpty() // true

priorityQueue.enqueue(1)
const empty2 = priorityQueue.isEmpty() // false