Read/Write Streams Example Code (for: http://loose-bits.com/2012/08/02/nodejs-read-write-streams-pipes.html)

.gitignore

out.txt

get.js

// Get Google's home page.
require('http').get("http://www.google.com/", function(response) {
  // The callback provides the response readable stream.
  // Then, we open our output text stream.
  var outStream = require('fs').createWriteStream("out.txt");

  // Pipe the input to the output, which writes the file.
  response.pipe(outStream);
});

nop.js

// Set both readable and writable in constructor.
var NopStream = function () {
  this.readable = true;
  this.writable = true;
};

// Inherit from base stream class.
require('util').inherits(NopStream, require('stream'));

// Extract args to `write` and emit as `data` event.
NopStream.prototype.write = function () {
  args = Array.prototype.slice.call(arguments, 0);
  this.emit.apply(this, ['data'].concat(args))
};

// Extract args to `end` and emit as `end` event.
NopStream.prototype.end = function () {
  args = Array.prototype.slice.call(arguments, 0);
  this.emit.apply(this, ['end'].concat(args))
};

// Download the same page again, but with the NOP stream
// in the middle.
require('http').get("http://www.google.com/", function(response) {
  var outStream = require('fs').createWriteStream("out.txt");

  response
    .pipe(new NopStream())
    .pipe(new NopStream())
    .pipe(new NopStream())
    .pipe(outStream);
});

upper-stream.js

#!/usr/bin/env node
/**
 * A simple upper-case stream converter.
 */
var UpperCaseStream = function () {
  this.readable = true;
  this.writable = true;
};

require("util").inherits(UpperCaseStream, require("stream"));

/**
 * Handle various params and upper-case string data.
 *
 * Signature can be in format of:
 *  - string, [encoding]
 *  - buffer
 *
 * Our example implementation hacks the data into a simpler
 # (string) form -- real implementations would need more.
 */
UpperCaseStream.prototype._transform = function (data) {
  // Here, we'll just shortcut to a string.
  data = data ? data.toString() : "";

  // Upper-case the string and emit data event with transformed data.
  this.emit("data", data.toUpperCase());
};

/**
 * Stream write (override).
 */
UpperCaseStream.prototype.write = function () {
  this._transform.apply(this, arguments);
};

/**
 * Stream end (override).
 */
UpperCaseStream.prototype.end = function () {
  this._transform.apply(this, arguments);
  this.emit("end");
};

/**
 * Test script.
 *
 * Read in this script, upper-case it, and write to "out.txt"
 */
function convertToUpperCase() {
  var fs = require("fs"),
    input = fs.createReadStream(__filename),
    output = fs.createWriteStream("out.txt"),
    upperCase = new UpperCaseStream();

  // Open our read input, uppercase it, then write out.
  input
    .pipe(upperCase)
    .pipe(output);
}

// Run script if directly executed.
if (require.main === module) {
  convertToUpperCase();
}