List Directories asynchronously in node.js.

We needed an easy way of listing all the directories in a project so we could watch them for changes.
We reviewed many available options and found them lacking in one of the following areas:

1. Untested (or incomplete tests)
2. Patchy documentation (often none)
3. Unmaintained or Abandoned (many open/unaddressed issues on GitHub)
4. Unclear code (written without shoshin)
5. Too Many Features trying to do too much. (we only need one thing a list of the directories)

Given an initial directory (e.g. the Current Working Directory) give me a list of all the "child" directories.

npm install listdirs --save

var listdirs = require('listdirs');
var basedir = __dirname; // or which ever base directory you prefer
listdirs(basedir, function callback(err, list){
    if(err){
      console.log(err); // handle errors in your preferred way.
    }
    else {
      console.log(list); // use the array of directories as required.
    }
});

If you have a large project and want to ignore the files in your .gitignore file (e.g. node_modules), there's an easy way to do this:

var listdirs = require('listdirs');
var ignored  = require('ignored')('./.gitignore'); // https://github.com/nelsonic/ignored
var basedir  = __dirname; // or which ever base directory you prefer
listdirs(basedir, function callback(err, list){
    if(err){
      console.log(err); // handle errors in your preferred way.
    }
    else {
      console.log(list); // use the array of directories as required.
    }
}, ignored); // include ignored list as 3rd Parameter (after callback)

Note: This example uses our ignored module: https://www.npmjs.com/package/ignored as an optional helper to list the entries in .gitignore file
but you can supply your list of ignored files as a simple array e.g: var ignored = ['node_modules', '.git', '.vagrant', 'etc.'];

The async (module) is good (as evidenced by its popularity!)
But way too many people use it as a crutch instead of understanding how to write their own asynchronous code.
We have deliberately avoided using async (the module) here, and as a result, listdirs is faster (we benchmarked it!) and includes less bloat.

We have included one dependency on isdir for the sake of splitting out code into "does-only-one-thing" (micro-modules) but isdir has zero dependencies so we know the stack!

As usual, a search on NPM (for list directories) returns many results:

A few of the modules we looked at before deciding to write our own:

• nodejs-walker: https://github.com/daaku/nodejs-walker unclear docs.
• dirtree: https://www.npmjs.com/package/dirtree comes really close to what we want! except it returns a tree object where we want a simple array.
• dirs: https://github.com/jonschlinkert/dirs unclear docs. uses async (=== lazy).
• dirlist: https://www.npmjs.com/package/dirlist (is a directory listing server - not a utility module)

Highly recommend reading the Unix Philosophy if you haven't already.

• 17 Unix Rules: http://en.wikipedia.org/wiki/Unix_philosophy#Eric_Raymond.E2.80.99s_17_Unix_Rules