淘宝电器的限时团购的时间是怎么做出来的？

Question

网址：http://3c.taobao.com/
怎么精确到毫秒，还有他好像不是用计时器做的，因为几乎没占CPU，如果用ＪＳ的计时器会很占CPU的

Answer 1

应该是js做的，禁用页面的js脚本，计数器就不动了。
没有占cpu不能说明不是js做的

Answer 2

的确是Js
可是我看了一下午没明白原理！！！
(function(){
                var U = YAHOO.util,Dom = U.Dom,Event = U.Event,
                dataCon = Dom.get('J_saleCountdown');
                if(!dataCon) return;                var bar = Dom.get('J_JoinBar'),
                show = Dom.get('J_JoinNum'),
                endTime = dataCon.getAttribute('data-startTime'),
                startTime = dataCon.getAttribute('data-beginTime'),
                serveTime = dataCon.getAttribute('data-serveTime'),
                sellerId = dataCon.getAttribute('data-sellerId'),
                auctionId = dataCon.getAttribute('data-auctionId'),
                lowest = dataCon.getAttribute('data-lowest')>>0,
                already=Dom.get("J_Already"),
                price=Dom.get("J_Price");
                function process(num){                    if(num >= 0){
                        already.innerHTML="<span>已团:<strong>"+num+"</strong>人</span><span >（最低人数:"+lowest+"）</span>"                    }else{
                        disable('系统异常，请重试');
                        already.innerHTML="<span >（最低人数:"+lowest+"）</span>"
                    }
                }                function dateFormat(d){
                    var d1=d.match(/^(\d{4})-(\d{1,2})-(\d{1,2}) (\d{1,2}):(\d{1,2}):(\d{1,2})/);
                    var d2=new Date();
                    d2.setFullYear(d1[1],d1[2]-1,d1[3]);
                    d2.setHours(d1[4],d1[5],d1[6]);
                    return d2;
                }                function timeDis(d1,d2){
                    if(!d1)d1 = dateFormat(endTime).getTime();
                    if(!d2)d2 = dateFormat(serveTime).getTime();
                    return d1 - d2;
                }                function disable(str){
                    str = str || '团购结束';
                    bar.innerHTML =""
                    Dom.get("J_Count_title").style.textIndent="-1000em"
                    Dom.get("sale-countdown").innerHTML=str
                    Dom.addClass(bar,'timeout');
                    bar.setAttribute('href','javascript:void(0);');
                }

Answer 3

function base64encode(str)
                {
                    str = utf16to8(str);
                    var out, i, len;
                    var c1, c2, c3;
                    var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
                    len = str.length;
                    i = 0;
                    out = "";
                    while(i < len)
                    {
                        c1 = str.charCodeAt(i++) & 0xff;
                        if(i == len){
                            out += base64EncodeChars.charAt(c1 >> 2);
                            out += base64EncodeChars.charAt((c1 & 0x3) << 4);
                            out += "==";
                            break;
                        }
                        c2 = str.charCodeAt(i++);
                        if(i == len)
                        {
                            out += base64EncodeChars.charAt(c1 >> 2);
                            out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
                            out += base64EncodeChars.charAt((c2 & 0xF) << 2);
                            out += "=";
                            break;
                        }
                        c3 = str.charCodeAt(i++);
                        out += base64EncodeChars.charAt(c1 >> 2);
                        out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
                        out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));
                        out += base64EncodeChars.charAt(c3 & 0x3F);
                    }
                    return out;
                }
                function utf16to8(str) {
                    var out, i, len, c;
                    out = "";    len = str.length;
                    for(i = 0; i < len; i++)
                    {
                        c = str.charCodeAt(i);
                        if ((c >= 0x0001) && (c <= 0x007F))
                        {
                            out += str.charAt(i);
                        } else if (c > 0x07FF) {
                            out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
                            out += String.fromCharCode(0x80 | ((c >>  6) & 0x3F));
                            out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));
                        } else {
                            out += String.fromCharCode(0xC0 | ((c >>  6) & 0x1F));
                            out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));
                        }
                    }
                    return out;
                }                function init(){                    var timer,uri;                    if(timeDis()>0){
                        var dEnd = dateFormat(endTime).getTime();
                        var dCur = dateFormat(serveTime).getTime();
                        timer = setInterval(function(){
                            if(timeDis(dEnd,dCur += 1000)<= 0 ){
                                disable();
                                clearInterval(timer);
                            }
                        },1000);                        uri = 'http://tbskip.taobao.com/json/group_auction.htm?auctionId={auctionId}&nick={sellerId}&startTime={startTime}&endTime={endTime}';
                        uri = uri.replace('{auctionId}',auctionId).replace('{sellerId}',base64encode(sellerId)).replace('{startTime}',startTime).replace('{endTime}',endTime) + '&t=' + new Date().getTime();
                        U.Get.script(uri,{
                            onSuccess:function(){
                                if(typeof DigiGroup == 'undefined') return;
                                process(DigiGroup.current>>0);
                                delete DigiGroup;
                            }
                        });
                    }else{
                        disable();
                    }
                }
                init();
            })()