Now we can change the style sheet

Now we can change the style sheet. Cool. We have a more personalized page. Excellent. But we don’t have a personalized site. The preference is only applied to the current page; when we leave the current page the preference leaves with us. This situation, however, can be rectified with a cookie.

To store a cookie we need another function to return the current style sheet. We also need two functions to store and read the cookie.

The implementation of this function is naive in the extreme, it asks a finder object (which we'll get to in a moment) to return every film it knows about. Then it just hunts through this list to return those directed by a particular director. This particular piece of naivety I'm not going to fix, since it's just the scaffolding for the real point of this article.

The real point of this article is this finder object, or particularly how we connect the lister object with a particular finder object. The reason why this is interesting is that I want my wonderful moviesDirectedBy method to be completely independent of how all the movies are being stored. So all the method does is refer to a finder, and all that finder does is know how to respond to the findAll method. I can bring this out by defining an interface for the finder.


First we loop through all the link elements in the document again. We then check whether the link is a style sheet. If it is, we check whether the style sheet has a title. This tells us that the style sheet is either preferred or alternative.

The last check is to see whether or not the style sheet is active. If all three checks return true, we have the current style sheet and we can return the title.

There is a w3c specified DOM Level 2 attribute, “disabled,” that is set to false when a style sheet is applied to the document. This attribute is correctly implemented in Mozilla, but unfortunately not in MSIE.

MSIE does have a proprietary HTML attribute, also called “disabled,” that applies to link elements. This attribute is initially set to false for all link elements.

To set the MSIE disabled attribute to match the DOM Level 2 disabled attribute, we can call the setActiveStyleSheet() function with the name of the preferred style sheet.

To find out which style sheet is the preferred style sheet, we need another function. Because this function is so similar to the getActiveStyleSheet() function I’m not going to explain how it works, but here is what it may look like: