Archive for the ‘The Blog’ Category

js4php: thanks!

Monday, April 15th, 2013

JS4PHP book is almost a wrap! It started as "well, I have this blog post, then I have these slides from this conference, how hard could it be to make it into a book form?" Pretty hard, turns out. I'm surprised every time. Takes a while, you get distracted by something shinier and so on... No such thing as "quick book project", for me, at least.

But it's almost ready to go, O'Reilly folks are optimistic it will be done in time for the Fluent conference in May (where I'm not speaking btw). The price on Amazon really makes me happy, I think $7.90 for a tech book is unheard of.

JavaScript for PHP developers

So anyway, just wanted to say thanks to people that helped with the book along the way.


First and foremost, big thanks and gratitude to my second-time reviewers who helped me with "JavaScript Patterns" before, the Three Musketeers and d'Artagnan, the ever-so-amazing Andrea Giammarchi, Asen Bozhilov, Dmitry Soshnikov and Juriy "kangax" Zaytsev. As with the previous book they helped me tremendously with their deep knowledge and experience with JavaScript, their attention to detail and technical accuracy above all. You'll see little notes in the book following bold general statements, these notes often come from one of these guys saying: "hmm, this is not entirely correct and not always true, because...". I am forever in debt to these four ridiculously talented developers who also happen to be great and friendly people.

Many thanks to Chris Shiflett and Sean Coates. They made sure the PHP side of things make sense, but what's more, this whole book started as a post on their PHPAdvent (now blog, followed by a talk at the ConFoo conference which Sean helps organize.

Next, thanks to the Facebook engineers that hang out on the JavaScript group. I posted an early draft there asking for comments. Three people even went through the whole thing and gave me invaluable feedback and further nitpicking, which is the best quality in a technical reviewer. Thanks to Alok Menghrajani, James Ide and Alex Himel.

Finally, thanks to Randy Owens who read the "early release" of the book and meticulously filed tens of errata reports.

Unit testing in AsciiDoc

Tuesday, February 12th, 2013

While finishing off this book, which I choose to write in AsciiDoc format, I really appreciate the time I took to write myself a handy little script for testing the little code examples. Because, something always gets wrong in the final steps of editing and is nice to have some automated assurance that you didn't break something stupid.

AsciiDoc or MarkDown or some other text setup is how technical books should be written. Or any books, really. Having clear plain text lets you focus on the content and not wrestle with Word formatting. And it's also easy to parse and test.

Code in AsciiDoc

The code blocks in AsciiDoc are easy to spot. They look like:

var a = 0xff;
a === 255; //:: true

Testing and linting

All you have to do in a little unit testing utility is to extract these clearly defined blocks and run them to make sure there are no silly syntax errors, creeping in in the very last edits.

But why stop with a syntax check? Why not also run jslint and also instrument and run the code and see any expected values. Asserts, in testspeak.

In my setup I did just that: lint with jshint, instrument the places where I know the expected values, lint these too (why the hell not?), run them and assert the expected values.


Here's how the output of the utility looks like:

$ node scripts/test.js 
passed: 362, skipped: 43
linted: 317, nolints: 45

Since this is a book with some educational bad examples, not everything can be linted. Or run for that matter.


I choose JSHint over JSLint as it allows more flexibility to relax the rules. Also it's a node module I can import.

var jslint = require('jshint').JSHINT;

These are my lint options:

// JSHint options need to be more relaxed because the book also
// points out bad patterns
var lintopts = {
  indent: 2,   // 2 spaces for indentation
  trailing: true, // disallow spaces at the end of a line
  white: true,
  plusplus: false, // allows ++ and --
  browser: true,   // assumes some common browser globals exist
                   // such as `document`
  node: true,  // assumes the code can run in node.js
               // and globals such as `global` are defined
  expr: true,  // ok to have expressions that seemingly do nothing
               // such as `a; // true` which the samples use to show
               // result values
  loopfunc: true, // allows definition of a function in a loop
                  // for educational purposes (in the part about closures)
  newcap: false,  // allows calling constructors (capitalized functions) 
                  // without `new`, again just for educational purposes
  proto: true,    // allows using `__proto__` which is great for understanding
                  // prototypes, although it's not supported in all browsers

And the lint function that lints a snippet of code:

// lint a snippet
function lint(snip) {
  // lint the snippet with all the options and have it assume
  // assert objext exists
  if (!jslint(snip, lintopts, {assert: false})) {

Instrumenting and executing a snippet

Execution is simple:

// run a snippet
function exec(snip) {
  // muck some stuff up and zap log()
  var mock = "function define(){}; function alert(){}; console.log = function(){};";
  try {
    eval(snip + mock);
  } catch (e) {

The instrumentation is a little more interesting.

I often write snippets like:

// assign
var a = 1;
// test
a; // 1

Now I need a little bit of marker that will tell the instrumentation that a; is a piece of code to execute and 1 is the expected value. I came up with //::

So the above becomes:

var a = 1;
a; //:: 1

I also like to add some more explanation besides the returned value. I use ,, for that. So:

var a = 1;
a; //:: 1,, as you'd expect

Instrumented, this becomes:

var a = 1;
assert.deepEqual("a;",  1, "Error line #2");

The line is the line in the book with all code and prose, so it's easy to find.

The special markup like //:: and ,, gets stripped by another script that I run before commit.

A few other features are: support for NaN which doesn't deepEqual to anything and expecting errors with assert.throws(..)

So I can write and test code like:

sum(21, 21); //:: 42
plum(21, 21); //:: Error:: plum() is not defined

(:: that follow Error is the same as ,,)


Number("3,14"); //:: NaN

So here's the code instrumentation:

// Add asserts
function prep(l, n) {
  var parts = l.split(/;\s*\/\/::/); // "//::" separates expression to execute from its result
  var nonspace = parts[0].match(/\S/);
  var spaces = nonspace === null ? "" : Array(nonspace.index + 1).join(" ");
  parts[0] = parts[0].trim();
  if (parts[1]) {
    var r = parts[1].split(/\s*(,,|::)\s*/)[0].trim(); // the result may have ,, or ::, ignore what's on the right
                                                       // e.g. //:: true,, of course!
                                                       // e.g. //:: ReferenceError::Invalid whatever
    if (r.indexOf('Error') !== -1) {
      // expect //:: Error to throw
      return spaces + 'assert.throws(function () {' + parts[0] + '; }, ' + r + ', "error line #' + n + '");';
    if (r === 'NaN') {
      // special NaN case
      return spaces + 'assert(isNaN(' + parts[0] + '), true, "error line #' + n + '");'
    // usual
    return spaces + 'assert.deepEqual(' + parts[0] + ', ' + r + ', "error line #' + n + '");';
  return l;


Dependencies, locals, options and the main parser loop is how it all begins/ends:

// dependencies where I can see them
var assert = require('assert');
var fs = require('fs');
var jslint = require('jshint').JSHINT;
// buncha local vars
var snip, rawsnip.....;
// short
var log = console.log;
// JSHint options 
var lintopts = {
  indent: 2,   // 2 spaces for indentation
  // ....
// read the book one line at a time
fs.readFileSync('book.asc').toString().split('\n').forEach(function(src, num) {
  // src is a line in the book
  // num is the line number

There are a few additional features at snippet-level:

Ability to continue from a previous snippet using --//-- at the top of the snippet delimiter

Let's declare a variable:

var a = 1;

And then another one:

var b = 2;

And let's sum

a + b; //:: 3

Ability to skip a non-working snippet using ////

var 1v;  // invalid

Ability to run in non-strict mode (because strict is default) using ++

var a = 012;
a === 10; //:: true

nolint option

assoc["one"]; //:: 1

Cleanup before commit

Cleaning up all instrumentation markers and hints for the lint and the tests (gist):

var clean = require('fs').readFileSync('book.asc').toString().split('\n').filter(function(line) {
  if (line.indexOf('/*nolint*/') === 0 || line.indexOf('/*global') === 0) {
    return false;
  return true;
  .replace(/--\+\+--/g, '--')
  .replace(/--\/\/--/g, '--')
  .replace(/--\/\/\/\/--/g, '--');

Github gist

Here's the test.js script in its entirety.

“defer” for IE7’s operation aborted error

Friday, September 9th, 2011

IE has this "operation aborted" problem (MSDN article) when you try to change your parent while it's not ready.

This is the example they give that causes this error:

        document.body.innerHTML+="sample text";

Turns out you can easily solve it by just adding a defer attribute to the script. This works just fine:

      <script defer>
        document.body.innerHTML+="sample text";

Demo page here

BTW, this operation aborted may bite you if you decide to append a script node to the body, like

var js = document.createElement('script');
js.async = true;
js.src = "";

So it's not a good idea to append to the body like this when you don't control the page you're adding this code to, although document.body seems to be always available even when the page doesn't have a <body> tag

Scripting Photoshop with JavaScript

Saturday, August 20th, 2011

Did you know you can script common Photoshop tasks with JavaScript? Now you do 🙂

IDE even

When you install PS it comes with a tool called ExtendScript Toolkit, which is an IDE to write scripts - with debugger, console to try stuff out etc.

To launch I just type "Extend" in Spotlight search. I'm guessing it's got to be somewhere in Program Files\Adobe on Windows too.

Here it is:

Getting started

As you can see on the screenshot, it's easy to get started.

app; // the Photoshop application
app.documents; // collection of open files/documents
app.documents[0]; // the first file
app.documents[0].name; // the first file's filename
app.documents[0].layers.length // how many layers in the doc

Running your script

There's a green "play" button in the IDE, it runs your script.

The directive:

#target photoshop

tells the engine that this is a photoshop script. Apparently you can script other Adobe products too.

If you don't have photoshop open, this directive will open it for you. Then it's all you - open a file, hide a layer, save, close, etc

Also if you save your script file with a .jsx extension, you can put in on the desktop and double-click it. Easy as pie.

And finally, if you put it in the appropriate directory (PSDIR/Presets/Scripts), it will show up in Photoshop menus under File -> Scripts


A *Yahoo* search will find the docs for you right here:

There's a scripting guide (nice) and a JavaScript reference (the exact object/method names).

There are also VBScript and AppleScript references in case you insist on writing non-portable scripts 🙂

Generating code

Getting started with a completely new API can be a little uphill-y walk. For me it was especially so when it comes to saving a file with all the options. Worry not, you can generate code too!

Check the scripting guide where it talks about "The ScriptListener Plug-In". It's a plugin that you already have, you just copy it to to the appropriate directory to activate it and then restart PS.

Then whatever you do in photoshop will generate code in a .log file on your desktop. Then you can go back and cleanup that file (it generates somewhat verbose code) and get the parts you need.

Example - Mojotune chords

So for this "JavaScript is Everywhere" talk I gave this year at OSCON (slides) I came up (with a friend's help) with a sample application that I ported to different environments.

The core of it is m.js (m as in mojo, m as in (data) model). It's a portable piece of JavaScript that knows a lot about guitar chords. I wanted to generate nice PNGs with the data from the chord model. So - Photoshop scripting.

The document template is shown here with three visible layers.

This is the guitar's neck and each dot is where you press. The template has a layer for each dot (each fret on each string), appropriately named:

The task is to get the chord configuration, show the corresponding layers and save the file with the chord name as filename.

So I did this manually (while recording the generated code): show a layer, save the file.

Show/hide layers

The generated code for showing a layer looked like an oddly indented piece of overhead:

/////// GENERATED - DON'T!

// =======================================================
var idShw = charIDToTypeID( "Shw " );
    var desc2 = new ActionDescriptor();
    var idnull = charIDToTypeID( "null" );
        var list1 = new ActionList();
            var ref1 = new ActionReference();
            var idLyr = charIDToTypeID( "Lyr " );
            ref1.putName( idLyr, "11" );
        list1.putReference( ref1 );
    desc2.putList( idnull, list1 );
executeAction( idShw, desc2, DialogModes.NO );

This goes out the door since it can be replaced with:

app.documents[0].layers.getByName('11').visible = true;

(11 means first fret on first string)

Save for web

The generated code for saving a PNG is even worse, but I simply reindented it and shoved in into a function and that was that.

function saveFile(filename) {
    // the following is mostly auto-generated by PS 
    var idExpr = charIDToTypeID( "Expr" );
    var desc14 = new ActionDescriptor();

    /// 200 more lines...

All the chords

Finally the part that I actually had to write myself.


#target photoshop
#include "../../lib/m.js"

Notice how easy it is to include a JS file, in my case the data model m.js?

Singe var pattern:

var data, 
    i, c, v, 
    layers = app.documents[0].layers;

The mojo object comes from m.js. How it works is not very important. The thing is it has a mojo.guitar.getChord() method. You give it a chord name and it returns an array - which fret needs to be pressed on each string.

// mojo.guitar.getChord('Am')
// returns [ignore, 0, 1, 2, 2, 0, x]

All we need to do then is loop though the array and show the layers. Then save the file (e.g. Am.png) and then hide the same layers so they don't interfere the next chord. So this is the end result which generates all the chords m.js knows about:

for (c = 0; c < mojo.prettytones.length; c++) {
    for (v = 0; v < mojo.allchords.length; v++) {
        chord = mojo.prettytones[c].split('/')[0];
        chord += mojo.allchords[v];
        data = mojo.guitar.getChord(chord);
        for (i = 1; i <= 6; i++) {
            layer = "" + i + data[i];
            layers.getByName(layer).visible = true;
        chord = chord.replace('#', '-sharp');
        saveFile('~/stoyan/mojo/chords/images/' + chord + '.png');
        for (i = 1; i <= 6; i++) {
            layer = "" + i + data[i];
            layers.getByName(layer).visible = false;

Run it and that's it - a bunch of PNG images are written.


  • mojotune.jsx - The final script
  • m.js - the data model ("Check out Guitar George, he knows all the chords" - Dire Straits)
  • images - the generated chord PNGs
  • JS everywhere: slides and code

And the winner is…

Tuesday, April 5th, 2011

In the previous post I announced that one person will win a copy of the Brazilian Portuguese translation of JavaScript Patterns. So here's the winner:


He wins a signed copy of "Padrões JavaScript". Waiting for your mailing address, Lou 🙂

Update: Lou Doesn't speak Portuguese, so he gets an English copy. The second winner is:


Update: Monty is not too proud of his Portuguese skills either, so third is


Asen is an awesome JavaScripter, who actually reviewed the book (thanks a million!) and he already has a copy. Next.


How I picked the winner

By writing some JavaScript in the console, of course.

The winner was to be randomly picked from all those who retweet my tweet or post a comment in the announcement. So I had to collect those.


The tweet page says there has been 27 retweets (worded a bit like 28, but looks like it's 27). The page only shows about 15 people though and I need all of them. Given how Twitter doesn't let you search older stuff, I was afraid it was too late. I had to check the API first. I was expecting I can hit a few URLs and get the data I need. Tough luck. All these auth keys, tokens, secrets and stuff got me floored.

Luckily Twitter's UI is also using the APIs. Checking the network traffic I was able to spot the request I need!

The URL is:
I only needed to change the count to something over 27, so I made it 30. Lo and behold I got the data!

The rest of the stuff I did in Safari's Web Inspector console.

Visiting the URL:

We have a JSON array as a document.

>>> var a = document.body.innerHTML
>>> a
"<pre style="word-wrap: break-word; white-space: pre-wrap;">[{"profile_link_color":"0084B4","verified":false,"not....]</pre>"

Safari puts all in a PRE behind the scenes, so this is how we get the data:

>>> var source = $$('pre')[0].innerHTML;
>>> source

eval() it:

>>> source = eval(source)
[Object, Object...]
>>> source.length

Sounds right. Now let's move all usernames into a new array using the new ECMA5 forEach fancy-ness:

>>> var all = [];
>>> source.forEach(function(e){all.push(e.screen_name)})
>>> all.length
>>> all
["jrfaqcom", "gustavobarbosa", "gabrielsilva", ...."vishalkrsingh"]

Blog comments

I had 4 comments on the original post. WordPress puts all comments in a div with class commentlist, so this allows us to grab all comments:

>>> var comments = $$('.commentlist cite a')
>>> comments.length

Now let's only grab the names, they are in the href's innerHTML:

>>> var all = [];
>>> comments[0].innerHTML
"Fabiano Nunes"
>>> comments.forEach(function(e){all.push(e.innerHTML)})
TypeError: Result of expression 'comments.forEach' [undefined] is not a function.

Eh? What? Oh, the list of HREFs is not an array but a NodeList:

>>> comments
<a href="" rel="external nofollow" class="url">Fabiano Nunes</a>
<a href="" rel="external nofollow" class="url">Gabriel Izaias</a>
<a href="" rel="external nofollow" class="url">João Rodrigues</a>
<a href="" rel="external nofollow" class="url">João Rodrigues</a>
>>> comments.forEach

So, list of nodes converted to array:

>>> comments =

Now forEach is usable:

>>> comments.forEach
function forEach() {
    [native code]
>>> comments.forEach(function(e){all.push(e.innerHTML)})

So we have a list of all names. Lets serialize it, so it can be pasted to the other window where we had the Twitter data.

>>> all
["Fabiano Nunes", "Gabriel Izaias", "João Rodrigues", "João Rodrigues"]
>>> JSON.stringify(all)
"["Fabiano Nunes","Gabriel Izaias","João Rodrigues","João Rodrigues"]"

(Simple array join and then string split will do too in this simple example)

All together

Back to the twitter window. Deserializing the comments array:

>>> comments = JSON.parse('["Fabiano Nunes","Gabriel Izaias","João Rodrigues","João Rodrigues"]')
["Fabiano Nunes", "Gabriel Izaias", "João Rodrigues", "João Rodrigues"]

Merging the two arrays

>>> all = all.concat(comments);
["jrfaqcom", "gustavobarbosa", ...."João Rodrigues"]
>>> all.length

Perfect. 31 entries. Just as many as the days in March when I announced it. So let's take the 19th array element to be the winner.

But shuffle the array a bit first.


Sorting the array by randomness. (I shuffled and reshuffled it three times, just because.)

>> all.sort(function() {return 0 - (Math.round(Math.random()))})
["ravidsrk", "anagami", "lpetrov", ...]

And the winner is:

>>> all[18]

“JavaScript Patterns” now in Brazilian Portuguese

Sunday, March 20th, 2011

Padrões JavaScript

I've been terrible at promoting this book. But that should change starting today 🙂

So today I got a copy of "Padrões JavaScript" - the Brazilian Portuguese translation of JavaScript Patterns. Happy, happy, happy!

Given that I already got two copies few weeks ago, kept one and sent one to my mom for her collection, I thought I should give this one away.

If you want to enter for a chance to win a signed copy of the Brazilian Portuguese translation of JavaScript Patterns, you can do one or more of the following:

  • Leave a comment below, or/and
  • Retweet this

That's it, shipping's on me. Boa sorte!

pssst, here are two PDFs: table of contents and about half of chapter 1 for you evaluation pleasure 🙂

Book is almost out

Saturday, September 4th, 2010

The JavaScript Patterns book is to be sent to the printer next week and will be available as expected (and mentioned on Amazon) on or before Sept 28. Yey!

Dunno who said: writers don't like to write, they like to have written. Exactly how I feel today.

And let me share a quote from my favorite Kurt Vonnegut along the same lines. The book is Bluebeard.

    She asked me what had been the most pleasing thing about my professional life when I was a full-time painter -- having my first one-man show, getting a lot of money for a picture, the comradeship with fellow painters, being praised by a critic, or what?
    "We used to talk a lot about that in the old days," I said. "There was general agreement that if we were put into individual capsules with our art materials, and fired out into different parts of outer space, we would still have everything we loved about painting, which was the opportunity to lay on paint."
    I asked her in turn what the high point was for writers -- getting great reviews, or a terrific advance, or selling a book to the movies, or seeing somebody reading your book, or what? She said that she, too, could find happiness in a capsule in outer space, provided that she had a finished, proofread manuscript by her in there, along with somebody from her publishing house.
    "I don't understand," I said.
    "The orgastic moment for me is when I hand a manuscript to my publisher and say, 'Here! I'm all through with it. I never want to see it again,' " she said.

So - whew!

Expect a more detailed post about the book (and the wonderful team of JS guru tech reviewers!), after all I have to start promoting it, don't I?

JavaScript includes and DOMContentLoaded event

Saturday, July 26th, 2008

My article about the non-blocking behavior of javascript includes was recently published on the YUI blog. Luke Chambers asked how does this method affect DOMContentLoaded event, so I gave it a shot.

The test examples are:

Basically, I added an event listener to document DOMContentLoaded event and to the onload events of every script, image and the document. I also exaggerated the loading time of scripts and images.


Normal script tag

js: Sat Jul 26 2008 15:53:33 GMT-0700 (Pacific Daylight Time)
DOMContentLoaded: Sat Jul 26 2008 15:53:33 GMT-0700 (Pacific Daylight Time)
img2: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img1: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img6: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img3: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img5: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img4: Sat Jul 26 2008 15:53:37 GMT-0700 (Pacific Daylight Time)
img8: Sat Jul 26 2008 15:53:40 GMT-0700 (Pacific Daylight Time)
img7: Sat Jul 26 2008 15:53:40 GMT-0700 (Pacific Daylight Time)
onload: Sat Jul 26 2008 15:53:40 GMT-0700 (Pacific Daylight Time)

DOM-included script

DOMContentLoaded: Sat Jul 26 2008 15:55:29 GMT-0700 (Pacific Daylight Time)
img1: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img2: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img6: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img4: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img3: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img5: Sat Jul 26 2008 15:55:32 GMT-0700 (Pacific Daylight Time)
img8: Sat Jul 26 2008 15:55:35 GMT-0700 (Pacific Daylight Time)
img7: Sat Jul 26 2008 15:55:35 GMT-0700 (Pacific Daylight Time)
script: Sat Jul 26 2008 15:55:39 GMT-0700 (Pacific Daylight Time)
onload: Sat Jul 26 2008 15:55:39 GMT-0700 (Pacific Daylight Time)

In any event, the document onload waits for the script, no matter how it's included.

Progress indicator by animating background position

Wednesday, July 23rd, 2008

This post experiments with different patterns for indicating progress, you know, those "loading...", "Please wait..." type of things. The progress is shown by using JavaScript to animate the CSS background position.

There's this cool site called, great for discovering new music (if they only agree to ban Foo Fighters, the site will be perfect). Discovering music but also discovering interesting web design patterns, as it turns out. shows a progress indicator when you click a song, as if the background shows how the song gets loaded. So I had to try implementing this myself and I also played with two other variants of the background animation.

Here's a video, a little screencast to demonstrate how the loading looks like:

Here are the three examples, take a look at the code, there are no external JavaScript libraries, just some do-it-yourself animation with setInterval()

Example #1 - filling the background

For this you get an image that is at least as long as the container you're about to animate. The height of the background image doesn't matter, could be just one pixel. Here's the image I used.

Ar the start of the animation, the background image is so to the left, it's invisible. At the end of the animation, the background fills out the whole container.

Run example #1

Example #2 - overflowing background

This is a modified version of the previous pattern. Once the background is filled the animation keeps going, so the background escapes from view. Then it's moved back at the beginning and the animation repeats.

Run example #2

Example #3 - dancing arrow

If you remember old radios, this pattern looks like you're playing with the dial. Here, the background image is different, just a small square basically. It gets repeated vertically. Here's the backgournd.

Run example #3

Literal Notations

Saturday, May 17th, 2008

A little something from my forthcoming book "Object-Oriented JavaScript" I thought would be nice to share.

Literal Notations
name literal constructor example
object {} new Object() {prop: 1}
array [] new Array() [1,2,3,'test']
regular expression
/pattern/modifiers new RegExp('pattern', 'modifiers') /java.*/img