setInterval-----倒计时
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>无标题文档</title><script type="text/javascript">var timeObj = {time : 0,time_desc : 0}var $ = function(_id) {return document.getElementById(_id);}var init = function() {timeRandom();showTime();timeObj.time_desc = setInterval("showTime();", 1000);}var timeRandom = function() {timeObj.time = parseInt(Math.random() * 10) + 5;}var showTime = function() {if(timeObj.time <= 0) {clearInterval(timeObj.time_desc);$("time").innerHTML = "Game over"return;}$("time").innerHTML = timeObj.time;timeObj.time --;}</script></head><body onload="init();"><div id="time"></div></body></html>?