Mike West — Web Application Developer

Scope in JavaScript

I’ve got a new article in the latest issue of Digital Web, diving deeply into JavaScript’s concepts of scope and execution context.

Scope in JavaScript was originally an ode to the single most useful piece of the Prototype framework — the bind method. I wanted to discuss in detail how bind makes it possible to have interesting and readable object-oriented code, while at the same time embracing event handlers and setTimeout to control your code’s execution. The issue is simply that event handlers execute your code in a context outside your objects, which makes the this keyword confusing at best, and flat-out wrong at worst. bind is an elegant solution to the problem, and the article concludes with a deep dive into a simplified version of that function to tease out exactly what it does, and how it works.

I found, however, that the article was mostly incomprehensible to those without a firm grounding in the issues of scope and execution context, and the lesser-known ways of manipulating execution context (apply and call). In an effort to give that audience something to sink their teeth into, I added a good amount of discussion of the basic concepts of scope, and what an execution context really means. I hope I’ve struck a good balance between the two, and that the article builds a solid foundation as it goes.

If you’re interested in this sort of thing, read Scope in JavaScript, and let me know what you think. The comments should be interesting. :)

• Posted: 12. September 2006