页面实时更新时间的JS实例代码

function startTime() {
                     var today = new Date(); //定义日期对象  
                     var yyyy = today.getFullYear(); //通过日期对象的getFullYear()方法返回年   
                     var MM = today.getMonth() + 1; //通过日期对象的getMonth()方法返回年   
                     var dd = today.getDate(); //通过日期对象的getDate()方法返回年    
                     var hh = today.getHours(); //通过日期对象的getHours方法返回小时  
                     var mm = today.getMinutes(); //通过日期对象的getMinutes方法返回分钟  
                     var ss = today.getSeconds(); //通过日期对象的getSeconds方法返回秒  
                     // 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  
                     MM = checkTime(MM);
                     dd = checkTime(dd);
                     mm = checkTime(mm);
                     ss = checkTime(ss);
                     var day; //用于保存星期（getDay()方法得到星期编号）
                     if (today.getDay() == 0) day = "星期日 "
                     if (today.getDay() == 1) day = "星期一 "
                     if (today.getDay() == 2) day = "星期二 "
                     if (today.getDay() == 3) day = "星期三 "
                     if (today.getDay() == 4) day = "星期四 "
                     if (today.getDay() == 5) day = "星期五 "
                     if (today.getDay() == 6) day = "星期六 "
                     document.getElementById('nowDateTimeSpan').innerHTML = yyyy + "-" + MM + "-" + dd + " " + hh + ":" + mm + ":" + ss + "   " + day;
                     setTimeout('startTime()', 1000); //每一秒中重新加载startTime()方法
                 }

                 function checkTime(i) {
                     if (i < 10) {
                         i = "0" + i;
                     }
                     return i;
                 }