获取样式的简单的函数封装

        var CSS = {
            getStyle:function(elem,name){//获取样式
                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"); 
                    name = name.toLowerCase(); 
                    var s = document.defaultView.getComputedStyle(elem,""); 
                    return s && s.getPropertyValue(name); 
                } else{ 
                    return null; 
                } 
            },
            getPageX:function(elem){//元素相对于整个文档的X位置
                return elem.offsetParent? elem.offsetLeft + CSS.getPageX(elem.offsetParent) : elem.offsetLeft;
            },
            getPageY:function(elem){//元素相对于整个文档的Y位置
                return elem.offsetParent? elem.offsetTop + CSS.getPageY(elem.offsetParent) : elem.offsetTop;
            },
            getParentX:function(elem){//元素相对于父亲的X位置
                return elem.parentNode === elem.offsetParent ? elem.offsetLeft : CSS.getPageX(elem) - CSS.getPageX(elem.parentNode);
            },
            getParentY:function(elem){//元素相对于父亲的Y位置
                return elem.parentNode === elem.offsetParent ? elem.offsetTop : CSS.getPageY(elem) - CSS.getPageY(elem.parentNode);
            },
            getPosX:function(elem){//元素相对于它的CSS容器的X位置 
                return parseInt(CSS.getStyle(elem,"left")); 
            },
            getPosY:function(elem){//元素相对于它的CSS容器的Y位置 
                return parseInt(CSS.getStyle(elem,"top")); 
            },
            setOpacity:function(elem,level){
                if(elem.filters){ 
                    elem.style.filters = 'alpha(opacity='+level+')'; 
                }else{ 
                    elem.style.opacity = level/100; 
                }                 
            }
        };