//计时器
var intDiff = parseInt(15);//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');
        intDiff++;
        if (intDiff >= 20) {
            clearInterval(timer);   //定时器清除；
            history.back(-1);
        }
    }, 1000);

}
$(function () {
    timer(intDiff);
});