I want to make my own custom CSS elements that will be handled by a js file of mine. Is this possible?
Here would be an example:
div {
rounded-corners:15px 15px
}
And then use Javascript to apply the styles for each browser for rounding corners.
Is there a way to do something like this?
EDIT
The point isn't to add a common support for browsers. I want to implement my own CSS things.
The answer is "no". While it is possible to easily get style values from stylesheets in Internet Explorer by accessing the currentStyle property, like so:
alert(myDiv.currentStyle['rounded-corners']);
//-> "15px 15px"
...other browsers don't support the currentStyle property, opting instead to support the W3C standard window.getComputedStyle(). getComputedStyle() doesn't include "expando" style properties in the outcome, which means your only option would be to iterate over the rules in each stylesheet instead, which could be an expensive procedure depending on how many stylesheets and rules you have. Obviously, you also lose out on the browser's cascading/computing.
IE9 and the latest versions of Firefox and Chrome all handle border-radius anyway.
And you can use CSS3 Pie to add support to older version of IE. No need to write your own script.
EDIT: I suppose you could write your own version of CSS3 Pie, but why would you want to?
CSS already has a property for rounded corners, called border-radius.
This is supported by virtually all browsers in current use. The only exception of any significance is IE8 and earlier.
The good news in this case is that IE8 can indeed be programmed to work the way you're asking. Other browsers cannot, but IE can, and this is lucky, as it's the one browser that needs it more often than most.
So the direct answer to your question is "sometimes". Most browsers drop the styles they don't support, but IE keeps them. It obviously don't do anything with them, but you can access them via the DOM, which means that you can do what you're asking.... but only really in IE.
In the case of rounded corners, there is already an excellent Javascript-based hack for it called CSS3Pie. This is open source, so you can examine their source code to learn how it's done.
The CSS3Pie code is quite complex though, so if you want a simpler example to work from, take a look at this older script which does the same thing a lot more simplistically. Easier to read, but not as functional. For real life use, use CSS3Pie, but for learning, this one is a better starting point.
For working with IE, I would suggest following the examples in these scripts to achieve what you're asking. For other browsers, you will have a much harder time.
border-radius. Also, you might want to check out something like css3pie.com to save you the trouble of implementing rounded corners in unsupported browsers.border-radius): there were some differences in early implementations, but that was quite a long time ago (Firefox 3.0); current versions of all browsers that support it are pretty much the same.