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;
}