js实现本地时间同步

HTML代码

1 <html>
2 <head>
3     <title>时间</title>
4     <meta charset="utf-8">
5 </head>
6 <body onload="getTime()">
7     <span id="nowDateTimeSpan" ></span> 
8 </body>
9 </html>

js代码

//时间
function getTime(){
    var ndate = new Date();
    var nyear = ndate.getFullYear();
    var nmonth = ndate.getMonth()+1;
    var nday = ndate.getDate(); 
    var nhour = ndate.getHours();
    var nminute = ndate.getMinutes();
    var nsecond = ndate.getSeconds();
    // 如果分钟或小时的值小于10，则在其值前加0，比如如果时间是下午3点20分9秒的话，则显示15：20：09
    nmonth=checkTime(nmonth);
    nday=checkTime(nday);
    nminute=checkTime(nminute);   
    nsecond=checkTime(nsecond);    
    document.getElementById('nowDateTimeSpan').innerHTML=nyear+"-"+nmonth+"-"+nday+" "+nhour+":"+nminute+":"+nsecond;
    document.getElementById('nowDateTimeSpan1').innerHTML=nyear+"-"+nmonth+"-"+nday+" "+nhour+":"+nminute+":"+nsecond;
    document.getElementById('nowDateTimeSpan2').innerHTML=nyear+"-"+nmonth+"-"+nday+" "+nhour+":"+nminute+":"+nsecond;
    document.getElementById('nowDateTimeSpan3').innerHTML=nyear+"-"+nmonth+"-"+nday+" "+nhour+":"+nminute+":"+nsecond;
    document.getElementById('nowDateTimeSpan4').innerHTML=nyear+"-"+nmonth+"-"+nday+" "+nhour+":"+nminute+":"+nsecond;   
    //setTimeout('getTime()',1000);//每一秒中重新加载startTime()方法
    function checkTime(i){   
        if (i<10){
            i="0" + i;
        }   
        return i;
    }
}