Web防止重复提交数据的方法

<SCRIPT LANGUAGE="JavaScript">
<!--
        //JS cookie
        defaultTime = 10000; //默认间隔时间10秒;
        function SetCookie(name,value)
        {
                var Days = 1;
                var exp  = new Date();
                exp.setTime(exp.getTime() + Days*24*60*60*1000);
                document.cookie = name + "="+ escape (value) + ";expires=" + exp.toGMTString();
        }
        function getCookie(name)
        {
                var arr = document.cookie.match(new RegExp("(^| )"+name+"=([^;]*)(;|$)"));
                 if(arr != null) return unescape(arr[2]); return null;

        }
        function checkTime(){
                var d = new Date();
                var now = d.getTime();
                var lastTime = getCookie('lastTime');
                if(lastTime == 'null' || (parseInt(lastTime)+defaultTime) < parseInt(now)){
                        SetCookie('lastTime',now);
                        alert('发送成功');
                }
                else alert('您发得太快!');
        }
//-->
</SCRIPT>
<button onclick="checkTime();">发送</button>