Convert a directory structure in the filesystem to JSON with Node.js

I have a file structure like this:

root
|_ fruits
|___ apple
|______images
|________ apple001.jpg
|________ apple002.jpg
|_ animals
|___ cat
|______images
|________ cat001.jpg
|________ cat002.jpg

I would like to, using Javascript and Node.js, listen to this root directory and all sub directories and create a JSON which mirrors this directory structure, each node contains type, name, path, and children:

data = [
  {
    type: "folder",
    name: "animals",
    path: "/animals",
    children: [
      {
        type: "folder",
        name: "cat",
        path: "/animals/cat",
        children: [
          {
            type: "folder",
            name: "images",
            path: "/animals/cat/images",
            children: [
              {
                type: "file",
                name: "cat001.jpg",
                path: "/animals/cat/images/cat001.jpg"
              }, {
                type: "file",
                name: "cat001.jpg",
                path: "/animals/cat/images/cat002.jpg"
              }
            ]
          }
        ]
      }
    ]
  }
];

Here's a coffeescript JSON:

data = 
[
  type: "folder"
  name: "animals"
  path: "/animals"
  children  :
    [
      type: "folder"
      name: "cat"
      path: "/animals/cat"
      children:
        [
          type: "folder"
          name: "images"
          path: "/animals/cat/images"
          children: 
            [
              type: "file"
              name: "cat001.jpg"
              path: "/animals/cat/images/cat001.jpg"
            , 
              type: "file"
              name: "cat001.jpg"
              path: "/animals/cat/images/cat002.jpg"
            ]
        ]
    ]
]

how to get this json data format in django views?(python)

Here's a sketch. Error handling is left as an exercise for the reader.

var fs = require('fs'),
    path = require('path')

function dirTree(filename) {
    var stats = fs.lstatSync(filename),
        info = {
            path: filename,
            name: path.basename(filename)
        };

    if (stats.isDirectory()) {
        info.type = "folder";
        info.children = fs.readdirSync(filename).map(function(child) {
            return dirTree(filename + '/' + child);
        });
    } else {
        // Assuming it's a file. In real life it could be a symlink or
        // something else!
        info.type = "file";
    }

    return info;
}

if (module.parent == undefined) {
    // node dirTree.js ~/foo/bar
    var util = require('util');
    console.log(util.inspect(dirTree(process.argv[2]), false, null));
}

My CS example (w/ express) based on Miika's solution:

fs = require 'fs' #file system module
path = require 'path' # file path module

# returns json tree of directory structure
tree = (root) ->
    # clean trailing '/'(s)
    root = root.replace /\/+$/ , ""
    # extract tree ring if root exists
    if fs.existsSync root
        ring = fs.lstatSync root
    else
        return 'error: root does not exist'
    # type agnostic info
    info = 
        path: root
        name: path.basename(root)
    # dir   
    if ring.isDirectory()
        info.type = 'folder'
        # execute for each child and call tree recursively
        info.children = fs.readdirSync(root) .map (child) ->
            tree root + '/' + child
    # file
    else if ring.isFile()
        info.type = 'file'
    # link
    else if ring.isSymbolicLink()
        info.type = 'link'
    # other
    else
        info.type = 'unknown'
    # return tree 
    info

# error handling
handle = (e) ->
    return 'uncaught exception...'

exports.index = (req, res) ->
    try
        res.send tree './test/'
    catch e
        res.send handle e

You can use the code from this project but you should adapt the code to your needs:

https://github.com/NHQ/Node-FileUtils/blob/master/src/file-utils.js#L511-L593

From:

a
|- b
|  |- c
|  |  |- c1.txt
|  |
|  |- b1.txt
|  |- b2.txt
|
|- d
|  |
|
|- a1.txt
|- a2.txt

To:

{
    b: {
        "b1.txt": "a/b/b1.txt",
        "b2.txt": "a/b/b2.txt",
        c: {
            "c1.txt": "a/b/c/c1.txt"
        }
    },
    d: {},
    "a2.txt": "a/a2.txt",
    "a1.txt": "a/a1.txt"
}

Doing:

new File ("a").list (function (error, files){
    //files...
});

The accepted answer works, but it is synchronous and will deeply hurt your performance, especially for large directory trees.
I highly encourage you to use the following asynchronous solution, it is both faster and non-blocking.
Based on the parallel solution here.

var fs = require('fs');
var path = require('path');

var diretoryTreeToObj = function(dir, done) {
    var results = [];

    fs.readdir(dir, function(err, list) {
        if (err)
            return done(err);

        var pending = list.length;

        if (!pending)
            return done(null, {name: path.basename(dir), type: 'folder', children: results});

        list.forEach(function(file) {
            file = path.resolve(dir, file);
            fs.stat(file, function(err, stat) {
                if (stat && stat.isDirectory()) {
                    diretoryTreeToObj(file, function(err, res) {
                        results.push({
                            name: path.basename(file),
                            type: 'folder',
                            children: res
                        });
                        if (!--pending)
                            done(null, results);
                    });
                }
                else {
                    results.push({
                        type: 'file',
                        name: path.basename(file)
                    });
                    if (!--pending)
                        done(null, results);
                }
            });
        });
    });
};

Example usage:

var dirTree = ('/path/to/dir');

diretoryTreeToObj(dirTree, function(err, res){
    if(err)
        console.error(err);

    console.log(JSON.stringify(res));
});