typescript-queue

TypeScript Queue

typescript-queue is a robust implementation of a queue data structure in NodeJS/TypeScript.

Features:

• all standard queue operations with familiar data structure naming (poll, peek, add, element, remove, size, etc)
• zero external dependencies
• comprehensive unit testing with full coverage, and extensive commenting/documentation
• support for useful applications like queueing asynchronous functions
• queue functions that return Promise objects (useful for scraping and API testing/automation)
• separate PromiseQueue implementation that supports async/await, async iteration with for await, and efficient caching for asynchronous peek/poll operations
• suitable for mission-critical applications, especially where npm supply chain security is of concern

Queue

A Queue<T> instance is a traditional queue that manages an underlying array of items conforming to the type T.

import { Queue } from 'typescript-queue'

const queue = new Queue<number>()
queue.add(5)
queue.add([1, 3])

// Standard peek/poll methods for retrieving the front item
queue.peek()   // 5
queue.poll()   // 5

// Same as poll, but throws an error if empty
queue.remove() // 1

// Same as peek, but throws an error if empty
queue.element() // 3

// Add items and switch directions any time
queue.add(10)
queue.add(20)
queue.add(30)
queue.useFILO()
queue.poll()   // 30
queue.useFIFO()
queue.poll()   // 10
queue.poll()   // 20

Iterating

Provides syntactic sugar for sequentially iterating through elements of the queue.

// Poll with a while loop
while (queue.size() > 0) {
	const item = queue.poll()
	// ... handle front item
}

// Poll with an iterator
for (const item of queue) {
	// ... handle item
}

PromiseQueue

A PromiseQueue<T> instance is a separate queue implementation for queueing Promise objects and asynchronous functions that produce Promise objects.

import { PromiseQueue } from 'typescript-queue'

// Queue any function that produces a `Promise` object
const makeRequest: Request = async (id: string): Promise<object> => {
	// ... return API response
}

const queue = new PromiseQueue<object>()

// Add some requests (subsequent parameters are passed to `makeRequest`)
queue.add(makeRequest, 'first-id')
queue.add(makeRequest, 'second-id')
queue.add(makeRequest, 'third-id')
queue.add(makeRequest, 'fourth-id')

// Get first two API responses in sequential order
const first = await queue.poll()
const second = await queue.poll()

// Get second two API responses in parallel
const [ third, fourth ] = await queue.batch(2)

Iterating

Provides syntactic sugar for sequentially iterating through elements of the queue and handling asynchronous delay.

// Poll with a while loop
while (queue.size() > 0) {
	const item = await queue.poll()
	// ... handle front item
}

// Poll with an async iterator
for await (const item of queue) {
	// ... handle item
}

Testing

Tests are in the /test directory. Each implementation has a corresponding .test.ts file that uses Jest to describe unit tests and handle validations.

jest
npm run test

You can also generate a code coverage report with jest --coverage or npm run coverage.

jest --coverage
npm run coverage

Coverage reports are generated into the coverage directory. Further open-source development is expected to maintain 100% coverage and be meaningfully verified by unit testing.

License

MIT