大家帮我看看这断代码内存怎么释放。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

    <title></title>

    <style type="text/css">

        </style>



    <script src="js/JsGrid/jquery-1.5.2.min.js" type="text/javascript"></script>



    <script type="text/javascript">

        function test() {

            var mytb = document.getElementById("tb");

            var r = null;

            var c = null;

            for (var i = 0; i < mytb.rows.length; i++) {

                r = mytb.rows[i];

                c = r.cells;

                //$(c[0]).empty();

                c[0].innerHTML = "<img  align='center' border='0' src ='images/zhuangtai_1.jpg'></img>";//内存不断增加

                //c[0].innerHTML = "如果是文字就可以释放？";//内存无改变。

                //$(c[0]).html("<img  align='center' border='0' src ='images/zhuangtai_1.jpg'></img>");

                //c[0] = replaceHtml(c[0], "<img  align='center' border='0' src ='images/zhuangtai_1.jpg'></img>");

            }

        }



        onload = function() {

            for (var i = 0; i < 200; i++) {

                var r = document.getElementById("tb").insertRow(0);

                var c = r.insertCell(0);

                c.innerHTML = "内存为什么释放不出来呢？"

            }

            setInterval(test, 1000);

        };



        //        function replaceHtml(el, html) {

        //            var oldEl = typeof el === "string" ? document.getElementById(el) : el;

        //            // 单纯innerHTML在IE中会稍微更快一些

        //            oldEl.innerHTML = html;

        //            return oldEl;



        //            var newEl = oldEl.cloneNode(false);

        //            newEl.innerHTML = html;

        //            oldEl.parentNode.replaceChild(newEl, oldEl);

        //            /* 因为我们只是从DOM中移除旧元素，所以返回一个新元素引用用作恢复 */

        //            return newEl;

        //        }

    </script>



</head>

<body>

    <input id="Button1" type="button" onclick="test()" value="button" />

    <label id="LabID">

    </label>

    <table id="tb">

        <tr>

            <td id="粤B">

            </td>

        </tr>

    </table>

</body>

</html>