queue2

library0.2.1jsnpmunverified

queue2.js v0.2.1 is a specialized Node.js queue data structure that combines unordered and ordered queuing with injection capabilities. Created by fent, it allows tasks to be executed concurrently with a configurable concurrency limit while supporting ordered processing through task injection. The first worker handles unordered tasks with an inject method to replace the current task with a sequence of ordered tasks. It requires Node >=4 and has no external dependencies. The package is in maintenance mode with no recent updates, and its API includes event emitters for error, drain, full, and empty events. It is a niche solution for specific use cases like asynchronous file reading with ordered subdirectory traversal.

storage

npm install queue2

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · QUEUE2

queue2

storagejavascriptv0.2.1

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Queue2

✓ import { Queue2 } from 'queue2'

✗ const Queue2 = require('queue2').Queue2;

ESM import is correct for modern Node. Default import does not exist; Queue2 is a named export.

Queue2

✓ const { Queue2 } = require('queue2');

✗ const Queue2 = require('queue2');

CommonJS require with destructuring works. Direct require returns the class as the module.exports, so 'const Queue2 = require('queue2');' also works, but destructuring is more explicit.

default

✓ import Queue2 from 'queue2';

✗ import { Queue2 } from 'queue2';

The package does not export a default. Only named export 'Queue2' exists. This import will result in undefined.

Creates a Queue2 with two workers and concurrency 2, pushes unordered tasks, and handles completion via callback and drain event.

import { Queue2 } from 'queue2'; const worker1 = (a, b, callback) => { // Simulate async work setTimeout(() => { callback(null, a + b); }, 100); }; const worker2 = (task, callback) => { // ordered processing console.log('Processing:', task); callback(null); }; const queue = new Queue2(worker1, worker2, 2); queue.push(1, 2, (err, result) => { if (err) throw err; console.log('Result:', result); }); queue.push(3, 4); queue.on('drain', () => { console.log('All tasks completed'); queue.die(); });

Debug

Known issues

gotchaIn first worker, calling both inject() and callback() will cause undefined behavior. When inject is used, callback must not be called.

fix

Check if this.inject was called before calling callback, or use inject only without callback.

affects: >=0.0.0

gotchapush() with a callback function as the last argument only works if the callback position matches the first worker's callback parameter. If first worker expects multiple data arguments, the callback must be the last data argument.

fix

Ensure the callback is the last argument matching worker1's callback position.

affects: >=0.0.0

deprecatedPackage is in maintenance mode; no updates since 2016. Node >=4 is required, may not work on newer Node versions without --experimental-modules.

fix

Consider migrating to modern alternatives like p-limit or async.queue.

affects: >=0.2.1

Errors

Common errors & fixes

TypeError: Queue2 is not a constructor

Incorrect import: using default import when package exports named export.

fix

Import with named import: import { Queue2 } from 'queue2';

Error [ERR_REQUIRE_ESM]: require() of ES Module not supported

Using CommonJS require on an ESM-only package or vice versa.

fix

Use dynamic import() for ESM: const { Queue2 } = await import('queue2'); or set type:"module" in package.json.

Unhandled 'error' event: [Error: ...]

Error occurred in a task without a push callback and no error event listener.

fix

Attach a listener: queue.on('error', (err) => console.error(err));

Upgrade

Version history

0.2.1latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

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Resources

githubgit://github.com/fent/queue2.js ↗

packagequeue2 ↗

homepagehttps://github.com/fent/queue2.js#readme ↗