Modules

Export one function

function MyMainFunction() {
}

function lessImportantFunction() {
}

// Replace the exports with main function
module.exports = myMainFunction;

// Additional functions can be tucked on main
module.exports.lessImportantFunction = lessImportantFunction;

// Functions for tests can be tucked on under test
module.exports.test = {
    privateFunctionToTest: privateFunction
}

Modules, how?

function require(name) {

    var source = findSource(name);

    var module = { exports: {}};

    (function(module, exports){
        eval(source);
    })(module, module.exports);

return module;

}

Popular Modules

• Underscore
• Request
• Async
• Coffeescript
• Express
• Socket.io
• Mocha
• Optimist

Streams

Stream Pipe

// The benefit of streams
readableStream.pipe(writableStream)

Event Emitter

var events = require('events');
var util = require('util');
Tapir = function() {

    this.eat = function(food) {
        if (isMeat(food))
            this.emit('error', new Error("I'm a vegetarian"));
        else
            this.emit('eating', food);
    }
};
// Set EventEmitter as Tapir's prototype
util.inherits(Tapir, events.EventEmitter);

Readable Stream

• event: data (One argument, a Buffer object.)
• event: end (received EOF or FIN)
• event: error (emitted with exception object – does not close stream)
• method: pause() (suggestion stopRead())
• method: resume() (suggestion startRead())
• member: readable, boolean
• method: forceClose() (close the underlying file descriptor) (suggestion close())

Readable Stream

Example

var fs = require('fs')
var file = fs.createReadStream('./file.txt')
file.on('error, function(err) {
    console.log('Error ' + err)
    throw err;
})
file.on('data, function(err) {
    console.log('Data ' + data)
})
file.on('end, function(err) {
    console.log('End ' + data)
})

Writeable Stream

• method: write(data) (Returns true if flushed)
• method: close() (Writes EOF or a FIN packet )
• event: drain (Emitted, when all data has been written)
• event: error (emitted with exception object – does not close stream)
• member: writable, boolean

Writable Stream

Example

var writestream = new stream.Stream()
writestream.writable = true
writestream.write = function (data) {
return true // true means 'yes i am ready for more data now'
// OR return false and emit('drain') when ready later
}
writestream.end = function (data) {
// no more writes after end
// emit "close" (optional)
}

writestream.write({number: 1})
// note: in node core data is always a buffer or string

Pipe, simplified

var readstream = new stream.Stream()
readstream.readable = true

readstream.on('data', function(data) {
var ready = writestream.write(data)
if (ready === false) {
    this.pause()
    writestream.once('drain', this.resume.bind(this))
}
})

readstream.on('end', function() {
writestream.end()
}) 

A Simple Proxy

var r = request.defaults({'proxy':'http://localproxy.com'})

    http.createServer(function (req, resp) {
    if (req.url === '/doodle.png') {
        r.get('http://google.com/doodle.png').pipe(resp)
    }
})

Questions

http://anders.janmyr.com

@andersjanmyr

anders.janmyr@jayway.com

Blogs

Config

http://goo.gl/sS8Kv

Finding

http://goo.gl/qQVsP