JQuery页面计时器

页面倒计时
html：

<div class="timer">
<strong id="minute">0分</strong>
<strong id="second">0秒</strong>
</div>

Jquery：
//计时器

var intDiff = parseInt(1800);//倒计时总秒数量 
function timer(intDiff) { 
    window.setInterval(function () { 
        var minute = 0, 
              second = 0;//时间默认值 
        if (intDiff > 0) { 
                minute = Math.floor(intDiff / 60); 
                second = Math.floor(intDiff) - (minute * 60); } 
        if (minute <= 9) minute = '0' + minute; 
        if (second <= 9) second = '0' + second; 
        $('#minute').html('<s></s>' + minute + '分'); 
        $('#second').html('<s></s>' + second + '秒'); 
        int  Diff--; 
        if (intDiff <= 0) { clearInterval(timer); //定时器清除；
        history.back(-1);
     } 
}, 1000); } 
$(function () { 
        timer(intDiff); 
});