javascript中清除cookie程序代码

<script type="text/javascript">
    var exp = new Date();
        // 设置过期时间
    exp.setTime (exp.getTime() - 1);
        // 清除，path是路径，domain是域
    document.cookie = ""+ "; expires="+ exp.toGMTString()+"; path=/; domain=.qttc.net";
</script>