next-generation package manager

by DuosDual

Duo is a next-generation package manager that blends the best ideas from ComponentBrowserify and Go to make organizing and writing front-end code quick and painless.

Install It

Install Duo straight from npm with:

$ npm install -g duo

Getting Started

To get started just write normal Javascript, requiring from GitHub as you need them:

var uid = require('matthewmueller/uid');
var fmt = require('yields/fmt');

var msg = fmt('Your unique ID is %s!', uid());

That matthewmueller/uid will pull the dependency straight from GitHub, without you needing to edit any package manifest file!

You can also require modules straight from your file system:

var modal = require('./modal/index.js');

Then use duo to install your dependencies and build your file:

$ duo index.js

Finally, drop a single <script> onto your page and you’re done!

<script src="build/index.js"></script>

Same goes for CSS! You can require dependencies and assets straight from GitHub or from the file system:

@import 'necolas/normalize.css';
@import './layout/layout.css';

body {
  color: teal;
  background: url('./background-image.jpg');

Then bundle up your CSS with duo:

$ duo index.css

And add your bundled-up stylesheet to your page!

<link rel="stylesheet" href="build/index.css">


  1. has first-class support for Javascript, HTML and CSS
  2. exposes a unix-y command line interface
  3. pulls source directly from GitHub with semantic versioning
  4. supports source transforms, like Coffeescript or Sass
  5. does not require a manifest


Duo was designed from the ground up to grow alongside your application, making your three main workflows incredibly simple:

  1. creating quick proofs of concept
  2. writing modular components
  3. building large web applications

I. Proofs of Concept

As developers, we often need to test out an idea or isolate a bug. One of the big issues with existing package managers is that you cannot use your package manager without a lot of boilerplate files like package.json or component.json.

Duo removes this boilerplate, letting you require packages straight from your source code:

var events = require('component/events');
var uid = require('matthewmueller/uid');

You can also include versions, branches or paths:

var reactive = require('component/reactive@0.14.x');
var tip = require('component/tip@master');
var shortcuts = require('yields/shortcuts@0.0.1:/index.js');

And the same goes for CSS with import:

@import 'necolas/normalize.css';
@import 'twbs/bootstrap@v3.2.0:dist/css/bootstrap.css';

You can even directly require .html or .json files:

var template = require('./menu.html');
var schema = require('./schema.json');

Duo will take care of the rest, transforming the .html into a Javascript string, and .json into a Javascript object.

When you’re ready to build your files, just run:

$ duo index.js index.css

The new files will be located in the newly created build/ directory, using the same structure as your project.

II. Components

A successful package manager needs to have a strong component ecosystem. Duo supports all of the existing Component packages out of the box. And, since Duo can load from paths, it supports many Bower packages too. There are even plans to support Browserify packages as well.

We’re hoping to bridge the gap between all the different package managers and come up with a solution that works for everyone.

To create your own public component, just add a component.json to your repository:

  "name": "duo-component",
  "version": "0.0.1",
  "main": "index.js",
  "dependencies": {
    "component/tip": "1.x",
    "jkroso/computed-style": "0.1.0"

And then publish your component on GitHub, so that others can install it by simply requiring it into their application:

var thing = require('your/duo-component');

If you’re coming from the Component community, you’ll notice that we no longer need to add scriptsstyles or templates. Duo handles all of this for you, walking the dependency tree like Browserify and including everything you need automatically, for both Javascript and CSS!

III. Web Applications

In order for a package manager to be truly useful, it needs to scale to accommodate building entire web applications. Once again, Duo makes this process seamless.

Duo allows for building multiple pages at once, so that you can split up your application into different bundles and keep your page assets slim. To build from multiple entry files, just pass more than one entry into duo:

$ duo app/home.js app/about.js app/admin.js

You can even use brace expansion:

$ duo app/{home,about,admin}/index.{js,css}

If Duo discovers an asset like an image or font along the way, it will automatically include it in your build/ directory. Say we have the following image in our CSS file:

@import 'necolas/normalize.css';

body {
  background: url('./images/duo.png');

Duo will symlink duo.png to build/images/duo.png, so that you can serve the entire build/ directory from your web server.


To see some more complex examples of Duo in the wild, check out any of these repositories on GitHub:


For more information, read through some of the resources put together by the folks in the Duo community:

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