获取当前时间显示在页面上并每秒刷新

<span id="clockTime"></span>
        <script>
            // 获取当前时间
        //jQuery             
        function startTime() {
                var clockTime = document.getElementById("clockTime");
                var date = new Date();
                var year = date.getFullYear(); //当前年份
                var month = date.getMonth(); //当前月份
                var data = date.getDate(); //天
                var hours = date.getHours(); //小时
                var minute = date.getMinutes(); //分
                var second = date.getSeconds(); //秒
                var time = year + "-" + checkTime((month + 1)) + "-" + checkTime(data) + " " + checkTime(hours) + ":" + checkTime(minute) + ":" +                 checkTime(second);
                clockTime.innerHTML = time;
                setTimeout('startTime()', 1000); //每一秒中重新加载startTime()方法
            }
            startTime();
            //补位 当某个字段不是两位数时补0
            function checkTime(str) {
                var num;
                str > 10 ? num = str : num = "0" + str;
                return num;
            }

            //js

            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('clockTime').innerHTML = yyyy + "-" + MM + "-" + dd + " " + hh + ":" + mm + ":" + ss + "  " + day;
                setTimeout('startTime()', 1000); //每一秒中重新加载startTime()方法
            }
            startTime();
            function checkTime(i) {
                if (i < 10) {
                    i = "0" + i;
                }
                return i;
            }
        </script>

参考网址：https://www.jianshu.com/p/2fcd8230b903