snippet.js

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

function rmrf(file, callback) {
  fs.stat(file, function(err, stat) {
    if (err) return callback(err);
    if (stat.isFile()) return fs.unlink(file, callback);
    
    var dir = file;
    
    fs.readdir(dir, function(err, files) {
      if (err) return callback(err);
      if (!files.length) return fs.rmdir(dir, callback);
      
      var runner = TaskRunner(function(err) {
        err ? callback(err) : fs.rmdir(dir, callback);
      });
      
      files.forEach(function(f) {
        runner.runTask(function(cont) {
          rmrf(path.join(file, f), cont);
        });
      });
    });
  });
}

function getFiles(dir, condition, callback) {
  var result = [],
      runner = TaskRunner(function(err) {
        callback(err, result);
      });
  
  function visit(dir) {
    runner.runTask(function(cont) {
      fs.stat(dir, function(err, stat) {
        if (err) return cont(err);
        if (!condition || condition.test(dir)) {
          result.push(dir);
        }
        if (stat.isFile()) return cont();
        fs.readdir(dir, function(err, files) {
          if (err) return cont(err);
          files.forEach(function(f) {
            visit(path.join(dir, f));
          });
          cont();
        });
      });
    })
  }
  
  visit(dir);
}

function TaskRunner(callback) {
  var remaining = 0,
      notified = false;
  
  function runTask(func) {
    remaining++;
    func(taskCompleted);
  }
  
  function taskCompleted(err) {
    if (notified) return;
    if (err) {
      notified = true;
      callback(err);
    } else if ((--remaining) == 0) {
      notified = true;
      callback();
    }
  }
  
  return {
    runTask: runTask
  };
}