The long sabbatical

Yes, after that first hyped-up post the Back-end Programmer had a meeting with Fate. No, not that Fate, the Fate that visits us from time to time with big gifts. I have been really busy during those couple of years, just not with the back-end (or front-end for that matter) staff. Instead I was busy with the project of my life.

But as we all know, all good things have to come to an end and so I am back. Full force! The force of a tornado, or a tsunami, or-or-or just, you know, a running faucet (don't laugh, you don't know how much damage it can cause!)

Anyway, Win 8 development is no longer my priority and I am still trying to figure out exactly what I want to learn next.

I started working in a french-speaking (or, as we say it here, francophone) environment, so I guess for now learning how to work in French is my biggest priority. But all along there will be technical challenges to be faced and I will use this space to share my experiences as I go along.

Right now I am working on a big-scale Windows Azure PaaS project and there are many head-scratching (or even head-bumping) moments.

But because of the different environment, there are also many organizational ... let's call them issues, and I will talk about those as well.

But let me first ask you a question. Have you been in a position where you are feeling comfortable in your job, not very stressed-out, going along with the flow? Have you ever been in a place so comfortable that your entire being starts itching to get out, to move on? Do you remember the feeling that you just HAVE to break out of it, to go out of this comfort zone, look for something ... new? Different. Refreshing. Challenging. New.

Yes? Then you know what I am talking about. I spent almost 10 years at my last company. I think that I actually broke some kind of record because in our industry no one stays at the same company for that long. Everyone moves on. But I stayed. Mostly because I was meeting new people, travelling to different places, helping different customers, solving a whole lot of different problems, It was awesome! It was new, all the time! It was exciting! Until it no longer was. Until it became a part of the big gray ball that that keeps on moving, day after day.

It wasn't the pressure, because it disappeared long ago. It was the boredom. Planes and airports became boring. The constant change became boring. The clients became boring. And I became just a cog in the machine. I wasn't making any difference any more. I needed to break out.

And then the phone rang. The head-hunter was actually extremely open about the offer. Everyone that I met was honest - the project is in trouble and we need help. We need YOUR help. We need YOU.

This was the reason why I took this new job. It wasn't the money (although it's not bad), it wasn't the benefits (although they are great), it wasn't the technology (although it's the future). It was the desire to make a difference. The need to get up from the comfy sofa. To wake up. To break out.

So, are you comfortable?

Unit testing Javascript- why and how

Big delay for this post - the back-end programmer got tangled up in, well, back-end stuff.
However, one of the beautiful properties of back-end code is that it is easily testable (if you make it so).

This made me thinking - up until now my basic Javascript skills did not include "unit testing". The benefits of testing Javascript are the same if you tested C#, Java, or Python code:

• test-driving your code leads to a better design
• good test coverage builds trust in the code
• good tests take the fear away - if a test breaks, you (should) know what went wrong and start over

The question is - how do I get those same advantages when I write the dreaded Javascript? What tools are there?

I looked at several libraries, but there are two that caught my attention.
QUnit is worth your attention if you are already familiar with any xUnit framework. The syntax is very intuitive, there are different asserts for almost anything. And it is supported by the jQuery team so there is a guarantee for quality. What I did not like was the lack of support for mocking. Sure, there are separate libraries for that, but I wanted something... simpler. The other thing that made me look for something else was the fact that I had to create HTML "containers" for my test suites - not a big fan of it.

The other one is Jasmine. At first it looks a bit.. weird. There are describe()-s, and it()-s, and you don't have asserts but expect()-ations. After a bit, though, it started to grow on me. For several reasons:

• There are a lot of expectations already implemented, but if you wanted something custom, you could create custom ones fairly easy with custom matchers.
• Mocking - comes out of the box in the form of "spies". And you can even mock setInterval and setTimeout.
• No need to create HTML "containers". Not that you couldn't.

That last one led me to another point - if I don't have a HTML file, how do I run my tests? Jasmine is (I am told) widely adopted by the Ruby community and there are (as I am told) gems that you could use to include your tests in your CI process.
For .Net - not so much. With a little exception - a Visual Studio add-on called Chutzpah. This add-on not only provides a headless browser for executing the tests, it also adds MSBuild targets. As I later discovered, it even supports QUnit tests. It is a valuable tool for integrating your Javascript tests into the development and build process.

Here I will not go into much more detail on how to set up your environment. Because when it's done, it's done. And aside from small tweaks you shouldn't need to touch it. But how exactly do you write your unit tests?

I will go back to the Conway's Game of Life examples from the last post.
Remember the Cell class? In the basic rules of GoL a cell can be either dead or alive:
Let's write the unit tests using Jasmine:

describe('Cell', function () {});

What I created with the snippet above is just the definition of something I called "Cell" (although I could have called it "The basic GoL cell"). So far this line in itself doesn't do anything except let us know that we are going to see a few tests about this "Cell".

describe('Cell', function () {
    it('is dead by default', function () {
        var cell = new Cell();
        expect(cell.IsAlive()).toBe(false);
    });
});

Now, it() defines our test - what we called "cell" should be dead. And you can see a very simple expect()-ation.

And there you have it. If you run this test against the Cell object, it should pass:

var Cell = function (isAlive) {
    var _isAlive = isAlive != undefined ? isAlive : false;

    this.IsAlive = function () {
        return _isAlive;
    };

    this.IsDead = function () {
        return !_isAlive;
    };
};

Cheers!

Doing OO - the JS Way!

I was fighting to understand how to do object-oriented design with Javascript for years and this week I finally think I'm onto something.

I keep seeing the same scenario almost every time I start a new project:
* Start simple, customer says. We don't need fancy UI, customer says. Just make it work on the back-end, let's not worry about async-shmasync.
* First delivery - beautiful, they say. But can we make a bit more pop-y, they say. Let's start by auto-updating the grid "dashboard" every 5 seconds.

So I start building a PageManager (I know, don't let me get started on the name). At first, it's only retrieving the dashboard. Then, I need to register any number of "widgets" that need to be updated async. After that - modal "dialogs", on-demand script loading, etc. It all goes (relatively) well until the third or fourth sprint where it becomes clear that it's all good and everything, but we need to do it a little bit differently in one specific section of the application.

And it was my brain-twister for a long time - how do I get to reuse what I already had in this PageManager and add on it or change it completely. In other words - how do I get to do my inheritance and overriding in Javascript? Is there even a way to do it?

Turns out there is. And it lies in the magic property of every object that is called prototype.

Now, when I set off to learn "proper" Javascript, I decided to take a classic problem and to use it to build a working solution. I chose Conway's Game of Life because it is simple enough to understand and design and yet gives me plenty of possibilities to experiment and learn.

So, the Game of Life consists of a rectangular plane where each cell is either dead or alive. This concept can be easily modeled with a simple class which has one boolean variable indicating whether the cell is dead or alive.

var Cell = function (isAlive) {
    var _isAlive = isAlive != undefined ? isAlive : false;

    this.IsAlive = function () {
        return _isAlive;
    };

    this.IsDead = function () {
        return !_isAlive;
    };
};

That looks pretty well and it works too. You can create new Cells, passing them the initial state. And when you ask them back whether they are dead or alive, they respond properly. Go on and try it now, if you want.

What if I want to create an alternate universe where the rules of the game remain the same:
- a living cell with 2 or 3 alive neighbors survives in the next generation
- a dead cell with exactly 3 alive neighbors springs to life

But in my universe once a dead cell is resurrected, it will be neither dead nor alive. It will be a Zombie, who can never die but will not count as alive when counting the poor souls.

Knowing a bit about the Javascript call hierarchy, my first attempt was this very simple code:

var ZombieCell = function () {

    this.IsDead = function () {
        return _isAlive;
    };
};

ZombieCell.prototype = new Cell();

Nothing too complicated, and it looks fine. With only one drawback - it doesn't actually work.
The first problem is that the _isAlive field is not visible from ZombieCell. Because it is, well, private!
The other problem is that the constructor logic is never executed. Not when you set the prototype and not even when you create zombie cells.

After a lot of experimenting and trying to find the best syntactic support (there isn't any), this is what I came up with.

var ZombieCell = function () {
    Cell.call(this, false);

    this.IsDead = function () {
        return false;
    };
};

ZombieCell.prototype = Object.create(Cell);

A few things worth noting:
- the prototype property has to point to a valid "instance". Since my base class has constructor parameters, I had to use Object.create() to get one
- although the prototype points to a valid base class instance, the construction logic is NOT inherited and has to be explicitly invoked using call()
- ZombieCell cannot see the private variable _isAlive. Because it is exactly this - private, which means it is not visible by anything else but the entity that declares it.

Start Simple - Equivalence is NOT Equality

If you, like me, come from a curly-brace language, Javascript has some surprises for you. And not all of them are nice.

One of the first face-palm moments I had with Javascript was with the equality operators. Or what I thought were the equality operators. Because, you see, in C++ and C#, == means "is equal to" and != means "is not equal to". And they are type-safe, so you can't easily shoot yourself in the foot (unless you overload them).

So you happily start using them churning out validation code until you realize there is something wrong - comparisons sometimes work, but sometimes don't. And they are not always transitive. What's is going on?

First, you have to be sure that you are comparing apples to apples. Are you really comparing numbers to numbers? Look closer:

Hmm. So comparing a number to its string representation works - magically. Neat, you think, it simplifies code. Then what about
Hey, that's really neat - automatic type conversion. But what if I don't want it? Is there a way to get rid of it?

Turns out there is. Because these two operators are not testing equality - instead they are testing equivalence.
In general numbers are equivalent to their string representation (as is NaN), but dates (Date objects) are not. null is equivalent to undefined but to nothing else.

Now, if I want true equality, there is one solution - the triple equal (===) and its triple non-equal buddy (!==). The previous examples then become


Next time you are chasing weird validation bugs, think whether:

• you are comparing the right things (numbers to numbers)
• you are comparing what matters (actual value vs string representation).

Rules of thumb to decide which one to use (work for me, feel free to use them or leave them)

• Good candidates for equivalence are cases where type conversion does not matter or is even welcome. Think integer-to-float comparisons. null-to-undefined is also a good candidate.
• Think hard what kind of input you receive in your routines. If it is whatever jQuery's val() is returning, you are better off parsing it to the target  type first and then deciding which one of the two approaches is best.
• In general avoid comparing anything to strings (unless it is also a string).

A lot of bugs and confusion can be avoided if you remember - equivalence is powerful, but it is not transitive. If a == b and b == c, it does not mean that a == c.

Equality is strict, but it is often more straight-forward, with less nasty surprises. And yes, if a === b and b === c, you are guaranteed that a === c.

The Beginning

I am starting this blog as a part of a new year's resolution - to start contributing to the programming community.

Recently I realized that I have many things to say, I just didn't know it. And I didn't know how to say it.
But now I know I can share what I know and it doesn't matter much how I do it. So a blog it is.

I come from a hard-core programming background. Back when I started, I was programming in C++ for Windows. Then the .Net Framework appeared and I started using it to create simple websites running on ASP.Net. Only after ASP.Net MVC became available I really grasped the power of the web. And it has been an adventure ever since.

This year my primary goal would be to learn mobile programming for Windows 8 using HTML 5 and Javascript.

Jump on the train with me to join the adventure!