JavaScript獲取css屬性的兼容寫法

 //注意：IE8及以下不支持querySelector也不支持getElementsByClassName
var imgbox=document.querySelector("#box");  

        function getStyle(elem,attr){
                    if(window.getComputedStyle){       //W3C
                        return window.getComputedStyle(elem,"")[attr]; 
                    }else if(elem.currentStyle){     //IE
                        return elem.currentStyle[attr];
                    }else{
                        return null;
                    }
                }

        alert(getStyle(imgbox,"height")) //[]裏面是要加引號的，所以height加引號傳進去