copytree.js

var fs = require('fs');
var path = require('path');
var sys = require('sys')
  , limit = 50
  , count = 0;

function copytree(src, dst) {
  if(!path.existsSync(src)) {
    throw new Error(src + ' does not exists. Nothing to be copied');
  }

  if(!fs.statSync(src).isDirectory()) {
    throw new Error(src + ' must be a directory');
  }

  var filenames = fs.readdirSync(src);
  var basedir = src;

  if(!path.existsSync(dst)) {
    fs.mkdirSync(dst, 0755);
  }
  var readNext = function(){
    if (!filenames.length) return;
    var filename = filenames.shift();
    console.log(filename);
    var file = basedir + '/' + filename;
    var newdst = dst + '/' + filename;

    if(fs.statSync(file).isDirectory()) {
      copytree(file, newdst);
      readNext();
    } else {
      count++;
      var reader = fs.createReadStream(file);
      var writer = fs.createWriteStream(newdst);
      writer.addListener('close', function(){
        count--;
        readNext();
      });
      sys.pump(reader, writer);
    }
  }
  readNext();
  while(count < limit) readNext();
}