iframe根据子frame的高度自动高度

<script type="text/javascript">
//光标移动到顶部
this.to_top=function(){
     $("html,body").animate({scrollTop:0}, 500);
}

this.setCwinHeight=function (iframeObj) {

        /*     8、获取iframe的高度
         iframe.contentWindow.document.body.offsetHeight;
         如果要获取iframe中的iframe
         document.getElementById('iframId').onload=function(){
         var html= window.frames["name属性"].frames["name属性"].document.getElementById('iframe中的元素的id').innerHTML;  

         $('#iframeId').load(function() { //方法1
         var iframeHeight = Math.min(iframe.contentWindow.window.document.documentElement.scrollHeight, iframe.contentWindow.window.document.body.scrollHeight);
         var h=$(this).contents().height();
         $(this).height(h+'px');
         });
         */
        if (document.getElementById) {
            if (iframeObj && !window.opera) {
                if (iframeObj.contentDocument
                        && iframeObj.contentDocument.body.offsetHeight) {
                    if (a = iframeObj.getAttribute("id") == "video_top") {
                        iframeObj.height = iframeObj.contentWindow.document.body.offsetHeight;
                    } else if (iframeObj.getAttribute("id") == "video_bottom") {
                        iframeObj.height = iframeObj.contentWindow.document.body.offsetHeight;
                    } else if (document.frames[0].contentWindow
                            && document.frames[0].contentWindow.document.body.scrollHeight) {
                        var height = document.frames[0].document.body.scrollHeight;
                    }
                }
            }
        }
    }
</script>

//src为子frame间接路径
<iframe id="video_bottom" src="${pageContext.request.contextPath}/vcomment/videoBottom/${videoId}.htm" width="90%"  frameborder="0" scrolling="no" onload="setCwinHeight(this);"></iframe>