example of stream2 new class

duplex.js

var Duplex = require('stream').Duplex;
var util = require('util');

function both() {
  if (!(this instanceof both)) return new both();

  Duplex.call(this);
}
util.inherits(both, Duplex);

both.prototype._read = function(size) {
  this.push('start read!');
  this.push(null);
};

both.prototype._write = function(chunk, encoding, cb) {
  if (chunk) { 
    this.push(chunk + ' write!');
  } else {
    this.push('empty write!');
  }
  cb();
};

var test = new both();
test.pipe(process.stdout);

test.on('end', function() {
  console.log('finish read! Let try write');
  process.stdin.pipe(test);
});

transform.js

var Transform = require('stream').Transform;
var util = require('util');

function append() {
  Transform.call(this);
}
util.inherits(append, Transform);

append.prototype._transform = function(chunk, encoding, cb) {
  this.push(chunk + '[ROCK]');
  cb();
};

var test = new append();
process.stdin.pipe(test).pipe(process.stdout);