More about node.js

Building maintainable node.js software

Streams all the way down!

Readable Stream

var Readable = require("stream").Readable var util = require("util") !function ICanRead(options) { Readable.call(this, options) this.data = ["I", "can", "read"] } util.inherits(ICanRead, Readable) !ICanRead.prototype._read = function(size) { var chunk = this.data.shift() this.push(chunk) } !var rs = new ICanRead({}) !rs.once("readable", function() { rs.pipe(process.stdout) }) !

Writable Stream

var Writable = require("stream").Writable var util = require("util") !function IConcatThings(options) { Writable.call(this, options) this.data = [] } util.inherits(IConcatThings, Writable) !IConcatThings.prototype._write = function(chunk, enc, done) { this.data.push(chunk) done() } !var cs = new IConcatThings({ objectMode: true }) cs.on("finish", function() { console.log(cs.data) }) cs.write(1) cs.write(2) cs.write(3) cs.end()

Transform Stream

var Transform = require("stream").Transform var util = require("util") !function ITransformThings(options) { Transform.call(this, options) this._writableState.objectMode = true this._readableState.objectMode = false } util.inherits(ITransformThings, Transform) !ITransformThings.prototype._transform = function(chunk, enc, done) { this.push(chunk.toString()) done() } !var ts = new ITransformThings() ts.pipe(process.stdout) ts.write(function(foo) { return foo }) ts.write("bar") ts.write([1,2,3]) ts.end()

Why streams are great

function httpHandler(req, res) { req.pipe(bodyParser) .pipe(shortner) .pipe(stringify) .pipe(res) }

Explicit error handling with streams

function httpHandler(req, res) { shortner.on("error", function(err) { res.statusCode = 500 res.end("Internal Server Error") }) ! req.pipe(bodyParser) .pipe(shortner) .pipe(stringify) .pipe(res) }

Ok just a quick thing build cat!

Debugging… because not all code is great :(

Seen that before?

def my_method a require "pry" binding.pry end !my_method "foo"

And this?

function myMethod(a) { debugger } !myMethod("foo")

using the node.js debugger