获取真实的样式值

function $(id){return document.getElementById(id);}            function getStyle(elem,name){                if(elem.style[name]){                    return elem.style[name];                    }else if(elem.currentStyle){                    return elem.currentStyle[name];                    }else if(document.defaultView && document.defaultView.getComputedStyle){                    name = name.replace(/([A-Z])/g,"-$1").toLowerCase();                    var s = document.defaultView.getComputedStyle(elem,'');                    return s && s.getPropertyValue(name);                    }else{                    return null                }            }            alert(getStyle($('box'),'height'));            alert(getStyle($('box'),'width'));