queue

asynchronous function queue with adjustable concurrency

   ____  __  _____  __  _____
  / __ `/ / / / _ \/ / / / _ \
 / /_/ / /_/ /  __/ /_/ /  __/
 \__, /\__,_/\___/\__,_/\___/
   /_/

Asynchronous function queue with adjustable concurrency.

Why

Async is a big library offering various approaches to dealing with asynchrony; queue is a small library offering a single, flexible abstraction.

This module exports a class Queue that implements most of the Array API. Pass async functions (ones that accept a callback) to an instance's additive array methods. Processing begins when you call q.start().

Install

npm install queue

Test

npm test npm run test-browser

Example

npm run example

var queue = require('queue');
 
var q = queue();
var results = [];
 
// add jobs using the Array API 
 
q.push(function(cb) {
  results.push('two');
  cb();
});
 
q.push(
  function(cb) {
    results.push('four');
    cb();
  },
  function(cb) {
    results.push('five');
    cb();
  }
);
 
q.unshift(function(cb) {
  results.push('one');
  cb();
});
 
q.splice(2, 0, function(cb) {
  results.push('three');
  cb();
});
 
// use the timeout feature to deal with jobs that 
// take too long or forget to execute a callback 
 
q.timeout = 100;
 
q.on('timeout', function(next, job) {
  console.log('job timed out:', job.toString().replace(/\n/g, ''));
  next();
});
 
q.push(function(cb) {
  setTimeout(function() {
    console.log('slow job finished');
    cb();
  }, 200);
});
 
q.push(function(cb) {
  console.log('forgot to execute callback');
});
 
// get notified when jobs complete 
 
q.on('success', function(result, job) {
  console.log('job finished processing:', job.toString().replace(/\n/g, ''));
});
 
// begin processing, get notified on end / failure 
 
q.start(function(err) {
  console.log('all done:', results);
});