A phenomena I'm seeing more and more of is Javascript code that is tied to a particular element on a particular page, rather than being tied to kinds of elements or UI patterns.

For example, say we had a couple of animated menus on a page:

<ul id="top-navigation">
    ...
</ul>

<!-- ... -->

<ul id="product-list">
    ...
</ul>

These two menus might exist on the same page or on different pages, and some pages mightn't have any menus.

I'll often see Javascript code like this (for these examples, I'm using jQuery):

$(document).ready(function() {
    $('ul#top-navigation').dropdownMenu();
    $('ul#product-selector').dropdownMenu();
});

Notice the problem?

The Javascript is tightly coupled to particular instances of a UI pattern rather than the UI pattern itself.

Now wouldn't it be so much simpler (and cleaner) to do this instead? -

$(document).ready(function() {
    $('ul.dropdown-menu').dropdownMenu();
});

Then we can put the 'dropdown-menu' class on our lists like so:

<ul id="top-navigation" class="dropdown-menu">
    ...
</ul>

<!-- ... -->

<ul id="product-list" class="dropdown-menu">
    ...
</ul>

This way of doing things would have the following benefits:

• Simpler Javascript - we only need to attach once to the class.
• We avoid looking for specific instances that mightn't exist on a given page.
• If we remove an element, we don't need to hunt through the Javascript to find the attach code for that element.

I believe techniques similar to this were pioneered by certain articles on alistapart.com.

I'm amazed these simple techniques still haven't gained widespread adoption, and I still see 'best-practice' code-samples and Javascript frameworks referring directly to UI instances rather than UI patterns.

Is there any reason for this? Is there some big disadvantage to the technique I just described that I'm unaware of?