priority-queue
functional, data oriented priority queue that doesn't suck
There are many priority queue implementations on the web, but I couldn't find any that meet these critera:
- does not allocate memory at run time
- has tests
- is functional, data oriented
- is tiny! (~150 lines of code)
- is a pure ES module
So here we are!
Usage
import PQ from 'priority-queue'
// create a new priority queue that can hold a maximum of 20,000 items.
// by default max length is 1000
const MAX_LENGTH = 20000
const obj = PQ.create(MAX_LENGTH)
// insert a few items
PQ.queue(obj, 'e', 1)
PQ.queue(obj, 'f', 9)
PQ.queue(obj, 'g', 4)
// get the highest priority item out of the queue
console.log(PQ.dequeue(obj)) // 'f'
console.log(PQ.dequeue(obj)) // 'g'
console.log(PQ.dequeue(obj)) // 'e'
// when the queue is empty it'll return undefined on dequeue
console.log(PQ.dequeue(obj)) // undefinedAPI
-
queue- add an element to the queue -
dequeue- delete the max priority element from the queue -
isEmpty- returns true/false -
clear- clear the queue -
delete- If we need to update the priority, delete that item and insert it in again -
list- contents of heap
Using classes/objects
class Box {
constructor(w, l) {
this.w = w
this.l = l
this.area = w * l // this is priority
}
}
const obj = PQ.create()
const a = new Box(5, 5)
const b = new Box(9, 9)
const c = new Box(2, 3)
const d = new Box(3, 3)
PQ.queue(obj, a, a.area)
PQ.queue(obj, c, c.area)
PQ.queue(obj, d, d.area)
PQ.queue(obj, b, b.area)
assert.deepEqual(PQ.dequeue(obj), b)
assert.deepEqual(PQ.dequeue(obj), a)