访问元素CSS属性

function getRealStyle(id, styleName) {
var element = document.getElementById(id);
var realStyle = null;
if (element.currentStyle) {
realStyle = element.currentStyle[styleName];
} else if (window.getComputedStyle) {
realStyle = window.getComputedStyle(element, null)[styleName];
}
return realStyle;
}