<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
body{background: RGB(222,222,2);}
</style>
</head>
<body>
<input type='button' value='点击按钮获取页面背景色' onclick="fun()"/>
<script type="text/javascript">
/*
＊javascript的style属性只能获取内联样式，对于外部样式和嵌入式样式*需要用currentStyle属性。但这种方法有兼容性（FF和Chrome不支持)
*/
HTMLElement.prototype.__defineGetter__("currentStyle", function() {
return this.ownerDocument.defaultView.getComputedStyle(this, null);
});
function fun(){
var color = document.body.currentStyle.backgroundColor;
alert(color);
}
</script>
</body>
</html>
