np-queue

中文文档
A queue to control Promise task's concurrency and pause/resume.

Install

npm i np-queue

Usage

import Queue from 'np-queue';
const q = new Queue();
const delay = (value) =>  
  new Promise(resolve => {
    setTimeout(() => resolve(value), 1000);  
  });

q.add(()=>delay(1)).then(console.log);
q.add(()=>delay(2)).then(console.log);

const delay_wrap = q.wrap(delay);

delay_wrap(3).then(console.log);
delay_wrap(4).then(console.log);

You will see it output 1,2,3,4 interval by 1 seconds.

NOTE: if in async function, you should not use await keyword, otherwise it will be running by "serial" because add() return a promise.

API

new Queue({concurrency})

concurrency

Limit how much Promise task can concurrency run, default is 1.

queue.add(fn,[key])

fn

The async function you define, it return a Promise or anything, note it will not receive any arguments so you must wrap your arguments in its code.

key

The task key you define, can use any type except undefined, if you give one key that already exist in queue, add() will return a rejection Promise.

queue.wrap(fn, [thisArg])

It will be return a function that wrap the fn, use the queue's concurrency to limit how much fn can be execute on same time.

For example, you can fast define one function it only can serial execute:

const serial_fn = new Queue().wrap(fn);

On many time it's useful.

queue.pause() & queue.resume()

Pause/resume this queue, no more word.

queue.all()

like Promise.all, waiting all queue's tasks promise be done, notice it may not sort by running order.

queue.concurrency

get/set queue's concurrency.

Test

npm run test