Pseudo-abstraction in Backbone

Thursday, May 2nd, 2013

As has been mostly disseminated, JavaScript, being a dynamic, prototypal language, affords developers the ability to design outside the rigid confines inherent to statically typed languages. Interestingly, perhaps even somewhat paradoxically, this same flexibility also allows for programmatically simulating specific features commonly found in statically typed languages, if desired.

While JavaScript does not have a traditional type system, nor does it provide traditional constructs by which user defined types are specified, it is still, necessarily so, a common and desirable design goal to implement a system with the notion of classes in order to provide data types which encapsulate domain logic and facilitate reuse; both of which being key design attributes which help mitigate the complexity of large applications.

Nearly all JavaScript MV* frameworks provide such facilities, and do so in a consistent and convenient manner; most of which allowing for practical circumvention of the prototype system almost entirely. It is also worth noting that while most libraries themselves are generally implemented in the succinct and terse, large applications typically call for a more traditional object oriented design, while also being prudent to do so in alignment with the conventions and idioms particular to JavaScript itself.


At times it will be necessary to design a system with reusable abstractions. In fact, it is quite hard to imagine a modern SPA of even marginal complexity as being maintainable without some level of base class functionality.

For instance, it can be particularly useful to implement base Models and Collections which provide general functionality common amongst all Models and Collections; such as the parsing and appropriate routing of service API exceptions to error callbacks, and successful service results to success callbacks, and so forth.

Since such base classes generally do not provide any concrete behaviors themselves (hence the abstraction), they are of considerable value, specifically when reused amongst various large scale, distributed projects; and, from a design perspective, it is often important for one to ensure such classes are only used as intended.

While one can convey the intended usage of a base class easily enough simply by means of comments alone, indicating their usage as such (and that is quite fine if you prefer), it is also just as easy to ensure base classes are only used as intended programmatically by implementing a simple conditional which checks an instance’s constructor against the base class’ constructor function. For example (in the context of backbone, though any framework applies):

Then, one can simply extend the base class, invoking defaults as needed:

Concluding Thoughts

Like many in the JavaScript community, I, too, am of the opinion that JavaScript should not be made to reflect that which is common to other languages simply for the sake of familiarity; but rather, one should be prudent to leverage the flexibility inherent to the language itself, and this example serves as a demonstration of how such flexibility can be utilized to provide what a specific design calls for at the discretion of the developer.

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