js实现倒计时

 ???//倒计时8分钟 ???var getTime=sessionStorage.getItem("zicetime"); ???var intDiff = parseInt(getTime * 60);//倒计时总秒数量 ???function timer(intDiff){ ???????window.setInterval(function(){ ???????var day=0, ???????????hour=0, ???????????minute=0, ???????????second=0;//时间默认值 ???????????????if(intDiff > 0){ ???????????day = Math.floor(intDiff / (60 * 60 * 24)); ???????????hour = Math.floor(intDiff / (60 * 60)) - (day * 24); ???????????minute = Math.floor(intDiff / 60) - (day * 24 * 60) - (hour * 60); ???????????second = Math.floor(intDiff) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60); ???????} ???????if (minute <= 9) minute = ‘0‘ + minute; ???????if (second <= 9) second = ‘0‘ + second; ??????// $(‘#day_show‘).html(day+"天"); ???????$(‘#hour_show‘).html(‘<s id="h"></s>‘+hour+‘时‘); ???????$(‘#minute_show‘).html(‘<s></s>‘+minute+‘分‘); ???????$(‘#second_show‘).html(‘<s></s>‘+second+‘秒‘); ???????intDiff--; ???????// if(intDiff==50){ ???????// ??alert(123) ???????// } ???????}, 1000); ???} ????$(function(){ ???????timer(intDiff); ???});