JavaScript实现记住密码功能

用js实现记住密码功能，但是前端记住密码不安全，最好还是不要用。我感觉这个记住密码应该是通过与后台建立一个会话来实现。
这个效果的测试地址在：http://ofoyou.com/blog/rePassword.html
<!DOCTYPE HTML>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>js COOKIE 记住帐号或密码</title>
    <script type="text/javascript">
    //点击登录时触发客户端事件
    function SetPwdAndChk() {
        //取用户名
        var usr = document.getElementById('txtUserName').value;
        alert(usr);
        //将最后一个用户信息写入到Cookie
        SetLastUser(usr);
        //如果记住密码选项被选中
        if (document.getElementById('chkRememberPwd').checked == true) {
            //取密码值
            var pwd = document.getElementById('txtPassword').value;
            alert(pwd);
            var expdate = new Date();
            expdate.setTime(expdate.getTime() + 14 * (24 * 60 * 60 * 1000));
            //将用户名和密码写入到Cookie
            SetCookie(usr, pwd, expdate);
        } else {
            //如果没有选中记住密码,则立即过期
            ResetCookie();
        }
    }

    function SetLastUser(usr) {
        var id = "49BAC005-7D5B-4231-8CEA-16939BEACD67";
        var expdate = new Date();
        //当前时间加上两周的时间
        expdate.setTime(expdate.getTime() + 14 * (24 * 60 * 60 * 1000));
        SetCookie(id, usr, expdate);
    }
    //用户名失去焦点时调用该方法
    function GetPwdAndChk() {
        var usr = document.getElementById('txtUserName').value;
        var pwd = GetCookie(usr);
        if (pwd != null) {
            document.getElementById('chkRememberPwd').checked = true;
            document.getElementById('txtPassword').value = pwd;
        } else {
            document.getElementById('chkRememberPwd').checked = false;
            document.getElementById('txtPassword').value = "";
        }
    }
    //取Cookie的值
    function GetCookie(name) {
        var arg = name + "=";
        var alen = arg.length;
        var clen = document.cookie.length;
        var i = 0;
        while (i < clen) {
            var j = i + alen;
            //alert(j);
            if (document.cookie.substring(i, j) == arg) return getCookieVal(j);
            i = document.cookie.indexOf(" ", i) + 1;
            if (i == 0) break;
        }
        return null;
    }

    function getCookieVal(offset) {
        var endstr = document.cookie.indexOf(";", offset);
        if (endstr == -1) endstr = document.cookie.length;
        return unescape(document.cookie.substring(offset, endstr));
    }
    //写入到Cookie
    function SetCookie(name, value, expires) {
        var argv = SetCookie.arguments;
        //本例中length = 3
        var argc = SetCookie.arguments.length;
        var expires = (argc > 2) ? argv[2] : null;
        var path = (argc > 3) ? argv[3] : null;
        var domain = (argc > 4) ? argv[4] : null;
        var secure = (argc > 5) ? argv[5] : false;
        document.cookie = name + "=" + escape(value) + ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) + ((path == null) ? "" : ("; path=" + path)) + ((domain == null) ? "" : ("; domain=" + domain)) + ((secure == true) ? "; secure" : "");
    }

    function ResetCookie() {
        var usr = document.getElementById('txtUserName').value;
        var expdate = new Date();
        SetCookie(usr, null, expdate);
    }
    </script>
</head>

<body>
    <form id="form1">
        <div>
            用户名:
            <input type="text" id="txtUserName" onblur="GetPwdAndChk()">
            <br> 密码：
            <input type="password" id="txtPassword">
            <input type="checkbox" id="chkRememberPwd" />记住密码
            <br>
            <input type="button" OnClick="SetPwdAndChk()" value="进入" />
        </div>
    </form>
</body>

</html>