function getstyle(obj, style) {    if(obj.currentStyle){        return obj.currentStyle[style] //ie下获取样式    }else {        return  document.defaultView.getComputedStyle(obj,null)[style]//谷歌，火狐下获取默认样式    }}var d=document.getElementsByClassName("demo")[0];console.log(getstyle(d,"width"));