Scripting

At some point when reading about scope in JavaScript, you may have come across the term hoisting. It’s often used in the context of variable or function definitions.

For example, consider the following code:

A trackback on one of my previous posts (yeah, trackbacks aren’t just for spam) alerted me to an interesting point brought up by a blogger named Matt Pass. In his post entitled Walnut, Meet jQuery Sledgehammer he politely explains why he feels it’s overkill to use jQuery in a simple tutorial post.

His main point is summarized in this quote: “Do you really need a 90k JavaScript library (and thats the minified version) to toggle the size of a menu?”

Maybe it’s just me. Maybe I’m a JavaScript debugging n00b, or maybe it’s my limited knowledge of Firebug.

While I fully support the use of unobtrusive JavaScript in all projects, I do find it has one weakness: Connecting the HTML element with the code that acts upon it.

If you’ve been coding JavaScript since the dark ages of the web, you’ll know that JavaScript used to be commonly implemented in an obtrusive fashion that mixed markup with behaviour, which made your code messy, and added extra code to every individual page rather than putting it in an external reusable file.

Here is a simple example:

Although the lack of cross-browser CSS selector support has caused a number of useful CSS selectors to go almost unnoticed, developers can still manipulate styles on their pages using some of these little-used selectors through jQuery.

Below I’ve prepared a simple table that describes a number of CSS selectors that are not cross-browser compatible, along with the jQuery syntax for each. The syntaxes are exactly the same as they would be in CSS, save for the jQuery wrapper (just remove $() and the quotes to get the CSS syntax), so using these selectors in jQuery will provide somewhat of a practice ground to prepare you for when they’re fully supported by all commonly-used browsers.

Every week this website gets about 700 unique visits from Google searches, mostly from people searching for solutions to problems with JavaScript and CSS. I’m flattered, and I hope I can continue to publish useful articles that will assist people and help with the exchange of ideas and techniques. One search phrase that leads surfers to my site pretty much every day is something along the lines of “getElementById explorer 7”.

If you type this phrase into Google, Impressive Webs currently comes in at around result 115. Not to mention the fact that the article that comes up doesn’t really address this issue directly. That’s not a very good ranking for that search phrase — yet somehow people are still finding one of my pages through that search.

It is obvious that developers — likely beginners — are having issues getting the proper results when utilizing the getElementById method available in JavaScript, particularly in Internet Explorer versions 6 and 7. And since the users seem to be searching through dozens of web pages looking for a solution to their particular problem, then obviously the pages discussing this JavaScript method are either too confusing or don’t specifically provide a practical solution.

Many aspects of JavaScript code development are taken for granted, and scope is really no different. Of course, in many cases where minimal code is required, variable scope (or function scope) is a non-issue. But if you’re planning to get into larger application development with JavaScript, then you need to understand at least the basics on scope in JavaScript.

Using some simple code examples, I’m going to run through the basics of scope and try to give beginning to intermediate JavaScript developers a better grasp of this very important concept.