<html>

<head>

</head>

<body>

    <span id="time"></span>

    <script>

        var timestamp = Date.parse(new Date())/1000;

        var time_old = Date.parse(new Date())/1000;

        timeAdd()

        /**

         * @purpose    :    计时器，自动加一秒

         * @time    :    2018-01-23

         * @author    :    daicr

        */

        function timeAdd(){

            document.getElementById('time').innerHTML = time_format(timestamp-time_old);

            timestamp +=1;

            setTimeout("timeAdd()",1000);

        }

        /**

         * @purpose    :    将时间戳格式化为 HH:ii:ss的格式

         * @time    :    2018-01-23

         * @author    :    daicr

        */

        function time_format(sec){

            var time_str = '';

            var hour = '';

            var minute = '';

            var second = '';

            if(sec < 0){

                time_str = '00:00:00';

            }else if(sec < 3600){        // 一小时以内

                // 分钟

                minute = Math.floor(sec/60);

                if(minute < 10){

                    minute = '0'+minute;

                }

                //秒

                second = sec%60;

                if(second < 10){

                    second = '0'+second;

                }

                time_str = '00:'+minute+':'+second;

            }else{                     // 一小时以上

                // 小时

                hour = Math.floor(sec/3600);

                if(hour < 10){

                    hour = '0'+hour;

                }

                // 分钟

                minute = Math.floor((sec%3600)/60);

                if(minute < 10){

                    minute = '0'+minute;

                }

                //秒

                second = sec%60;

                if(second < 10){

                    second = '0'+second;

                }

                time_str = hour+':'+minute+':'+second;

            }

            return time_str;

        }

    </script>

</body>

</html>