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The capabilities of CSS increase all the time, and more “interactive” features are constantly being added to the CSS specification.
If we move the cursor to the extreme bottom-right of the viewing area, we want the big image to move by almost its entire size — but not quite! When a page is scrolled, the specification is rather vague on whether clientX and clientY are returned relative to the whole document, or to the window the part of the document that is visible. When the link is clicked, it will fire a click event, and that code will run. Similarly, a browser that implements the DOM completely and without bugs would make life very easy.
Processing happens as follows.
Each browser fixes malformed content in a different way, which can generate such horrors as an element that is its own parent node. We then create the text node for the text that will appear inside the link. Some users find this useful; others find it heartily annoying. Keeping your HTML valid avoids all these problems.
It has a real wow factor! This technique for checking that something exists is called feature sniffingand will be explained in more detail in the next chapter. You can find them in the weg archive for this book. Its structure reflects our earlier discussions, but it contains some additional code for this particular technique.
Thus, using valid HTML gives you more time to spend with your family, play snooker, etc. It would be nice to be able to grab the Yahoo! Another step to CSS guru-hood is understanding exactly what each browser does wrong, and how you can work around those failings. Although the full definition of CSS allows you to do some fairly amazing things, and to control the presentation of your pages to a high degree, not every browser supports everything that CSS has to offer.
We can safely assume in the image check that link.
We might use the following code:. Websites are written in HTML. The core of DHTML — the D-for-dynamic bit — lies in our ability to change those elements, to remove them, and to add new utkpia. Since a className is a string, it has all the methods of a string, one of which is replace ; we can call the replace method with a regular expression first parameter and a substitute string second parameter.
HTML that complies with these rules is said to be “valid. This is a slightly suspect technique: We use it to call the addListeners function once the page has loaded. While the set of rules is pretty complex, you can ensure that your HTML is valid by following a few simple guidelines. What has changed is the way in which this listener is assigned. For now, simply remember that if you cross your tags, each browser will interpret your code in a different way, according to different rules rather than according to the standard.
The only way to do it in Safari at least until Apple fixes its DOM standard event support is to dntml an old-style event handler that returns false. Badly implemented standards are a bigger problem.
The second function makes sure that the first is connected to the right HTML tag. Now, what should appear when the cursor is located at the bottom-right corner of the viewing area? You might have noticed above that I used mouseover, rather than onmouseoverfor the event name.