Reading non-inline CSS style info from Javascript

I know I must be missing something here, but I cannot seem to get this to work.

I have assigned a background color to the body of an html document using the style tags inside the head section of the document, but when I try to read it via JavaScript, I get nothing:

<html>
<head>
<style>
body { background-color: #ff0; }
</style>
</head>
<body>
<a href="#" onclick='alert(document.body.style.backgroundColor)'>Click Here</a>
</body>
</html>

.. however, if I assign the style inline, it works:

<html>
<head></head>
<body style='background-color: #ff0;'>
<a href="#" onclick='alert(document.body.style.backgroundColor)'>Click Here</a>
</body>
</html>

I know I am missing something basic, but my mind is not in the zone today -- can anyone tell me why my first scenario is not working?

Thanks

Answers:

Answer

The style property of a DOM element refers only to the element's inline styles.

Depending on the browser, you can get the actual style of an element using DOM CSS

In firefox, for example:

var body = document.getElementsByTagName("body")[0];
var bg = window.getComputedStyle(body, null).backgroundColor;

Or in IE:

var body = document.getElementsByTagName("body")[0];
var bg = body.currentStyle.backgroundColor;
Answer

In this case, you'll want the computedStyle on the Element as the style attribute hasn't been set yet. In IE, you'll need to check the Element's currentStyle property, via something like this.

Answer

Here is a function you can use (without the use of a framework ie) that was posted here by InsDel:

function getStyle(className) {
    var classes = document.styleSheets[0].rules || document.styleSheets[0].cssRules
    for(var x=0;x<classes.length;x++) {
        if(classes[x].selectorText==className) {
                (classes[x].cssText) ? alert(classes[x].cssText) : alert(classes[x].style.cssText);
        }
    }
}
getStyle('.test')
Answer

That's just how css works. There's no straight-forward way to get the computed css attributes of an element within Javascript, that I know of, short of browser specific utilities.

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