pjobs

pjobs

A simple, efficient and small (just 2.8kb) queue job executor using promises with concurrency control. And some promise's utilities.

install

npm install --save pjobs

usage

queuePromises

defines an executor for jobs. A job is just a function that returns a Promise. You can also control concurrency and promises. Demonstration

import { queuePromises } from 'pjobs'
const queue = queuePromises({ 
  concurrency: 1, // maximum of promises running concurrently
  onProgress (status) { // allow you to inform users about execution progress
    console.log('queue status: ', status)
  }
})
queue.enqueue(async () => { // add a job to the queue
  console.log('task 1')
})
const promiseForTask2 = queue.promise(async () => { // add another job but returns a promise to this
  console.log('task 2')
  return 'OK'
})

await queue.waitFor() // wait for all jobs to be finished.
await promiseForTask2 // returns 'OK'

await queue.forEach(['task 3', 'task 4'], async (item) => {
  console.log(item) // works similar to Array.forEach
})

const doubles = await queue.map([1,2], async (item) => {
  return item * 2 // works similar to Array.map
})

const sum = await queue.reduce([1,2,3,4], async (ret, item) => {
  return item + ret // works similar to Array.reduce
  // When concurrency is one, items are processed sequentially. If concurrency is greater, the order of processing will variate
}, 0)

const two = await queue.some([1,2,3,4], async (item) => {
  return item % 2 === 0 // works similar to Array.some returns then found item or undefined
  // 4 is not returned because concurrency is 1. If concurrency is greater, the return value could be 2 or 4
})

defer

allow you to deferred promise. Like promise-deferred NPM but lighter.

import { defer } from 'pjobs'

const deffered = defer<number>()
setTimeout( ()=> deffered.resolve(1), 10) // 
setTimeout( ()=> deffered.reject(new Error('timeout')), 100)
await deffered.promise

sleep

allow you pause execution flow for some miliseconds

import { sleep } from 'pjobs'
await sleep(100) // pauses execution flow for 100 miliseconds

asap

delay execution of a function to as soon as possible

import { asap } from 'pjobs'
asap(()=>console.log('b')) // 'b' will be logged after 'a'
console.log('a');