Milk, Cookies & SegFaults…

Tag: OOP

  • Universal getter for plain JS objects.

    Many times in JavaScript we have to reach deep into objects to access fields that could possibly not be there at all; for example let’s assume I have a JS object called options into which I’ve just read an entire JSON configuration file. Trying to access a field like options.application.cache.enable directly will potentially fail (e.g. when any of the intermediate levels is missing)…

    if (options.application.cache.enable) {
    // do stuff
}

    …therefore this kind of work will usually involve some kind of testing for the existence of each level, so as to gracefully handle any misbehaving data. Also, many times I’ve seen the following approach used in these scenarios which is quite bad for anything more than a single depth level:

    if (options && options.application && ...) {
    // do stuff
}

    So, just as a little helper, here is a small method that may prove to be quite handy when having to deal with data whose structure we’re not certain of (here’s a proper Gist entry).
    (more…)

  • JS classes for the masses.

    Following on an older post of mine, I decided to write a new article about an(other) implementation of OOP Classes in JavaScript. This is something that brings a lot of value from very few lines of code and I want to share it with everyone and see how it can be improved.

    First let’s see the code (you should check here for the latest version) and then I’ll try and explain the relevant benefits/features but jump straight to the goodies if you like, knock yourself out! 🙂

    /**
 * Class.js: A class factory.
 */
function Class(members) {

    // setup proxy
    var Proxy = function() {};
    Proxy.prototype = (members.base || Class).prototype;

    // setup constructor
    members.init = members.init || function() {
        if (Proxy.prototype.hasOwnProperty("init")) {
            Proxy.prototype.init.apply(this, arguments);
        }
    };
    var Shell = members.init;

    // setup inheritance
    Shell.prototype = new Proxy();
    Shell.prototype.base = Proxy.prototype;

    // setup identity
    Shell.prototype.constructor = Shell;

    // setup augmentation
    Shell.grow = function(items) {
        for (var item in items) {
            if (!Shell.prototype.hasOwnProperty(item)) {
                Shell.prototype[item] = items[item];
            }
        }
        return Shell;
    };

    // attach members and return the new class
    return Shell.grow(members);
}

    Observations

    Each Class points to (via .prototype) a corresponding Proxy object that holds the class’s member fields. In turn, this Proxy points to (via .prototype) the Proxy of the inherited class (i.e. the super-Class) and so on. So, each Class points to its own Proxy which points to the ancestor Proxy and so on, until the top level ancestor is reached. (more…)

  • A simple(r) approach for class-based OOP in JavaScript.

    Like others before me, I found JavaScript’s prototype-based OOP support – while very powerful – quite cumbersome in some situations where I needed a certain structure or hierarchy of objects, situations in which one quickly comes to the conclusion that the best answer would be the concept of a Class.

    However, while I am well aware that the web is filled with various implementations of classical (i.e. class-based) object orientation in JavaScript, I can not help the feeling that they are over-engineered and over-complicated without need, quite often attempting to provide more functionality than is actually necessary. In short, I don’t feel they’re “classical” at all.

    This is why I started working on my own implementation of classical OOP  in JavaScript, which is shown below. Currently this is only a proposal, although I already started using it in one of my projects. Anyway, let’s look at it first then I’ll try and explain how it works.

    The Code

    /** Class factory. */
function Class(members) {

    // proxy constructor
    var Proxy = function() {
        for (var item in members) {
            this[item] = members[item];
        }
    };

    // proxy inheritance
    Proxy.prototype = (members.base || Class).prototype;

    // class constructor
    var Build = members.init || function() {};

    // class inheritance
    Build.prototype = new Proxy();
    Build.prototype.base = Proxy.prototype;
    Build.prototype.constructor = Build;

    // ready
    return Build;
}

    That is all, and this little function can have a whole world of nifty consequences like deep inheritance or access to the super-class via this.base (and others). But here is what happens: the basic principle at work here is the Proxy object, which essentially, contains all the members of our new class (the ones that are passed to the Class factory function as the members parameter). (more…)