function countd(){	var endTime='2017/01/20';//设置结束时间	var endT=new Date(endTime);	var newTime=new Date();	var count=endT.getTime()-newTime.getTime();	var day=Math.floor(count/1000/60/60/24);	var hours=Math.floor(count/1000/60/60%24);	var minute=Math.floor(count/1000/60%60);	var seconds=Math.floor(count/1000%60);	var body=document.getElementsByTagName('body')[0];//获取放置倒计时的标签	body.innerHTML=day+'天'+hours+'时'+minute+'分'+seconds+'秒';}setInterval(countd,1000);//设置定时器