我可以使用jQuery访问不存在或无效的CSS属性吗？

Question

There are 2 parts to this question:

1. If I define a CSS transition and try to access it with jQuery's .css() method, can I reliably assume that if the browser I'm running on does not support that CSS property it will always return undefined ?

2. If I DON'T define a CSS property and try to access it with jQuery's .css() method, can I reliably assume that it will always return undefined ?

Answer 1

The short answer is, #1. yes. #2. No.

The long answer is: #1. yes, you can make up a classname to test this, for example:

browser-foo: blue;

http://jsfiddle.net/32dzN/1/

If you haven't already, check out Modernizr. They provide excellent feature detection, I believe they put it into a DOM element off the screen if I recall correctly.

As for #2, that's not how it works at all. Because there are computed styles, as well as defined styles. For example, if you try to get the opacity of an element that you haven't set opacity on, it will return as 1.