JavaScript实现学生在线做题计时器功能

<div class=\"panel panel-default\">
 <label>答题计时：</label><input type=\"text\" name=\"\"
 readonly=\"readonly\" id=\"timer\" style=\"border: none;\">
</div>

<  type=\"text/ \">
var n_timer = timer();
//计算学生的做题时间
 var ele_timer = document.getElementById(\"timer\");
 var n_sec = 0; //秒
 var n_min = 0; //分
 var n_hour = 0; //时
 
 //60秒 === 1分
 //60分 === 1小时
 function timer() {
 return setInterval(function () {
 
 var str_sec = n_sec;
 var str_min = n_min;
 var str_hour = n_hour;
 if (n_sec < 10) {
 str_sec = \"0\" + n_sec;
 }
 if (n_min < 10) {
 str_min = \"0\" + n_min;
 }
 
 if (n_hour < 10) {
 str_hour = \"0\" + n_hour;
 }
 
 var time = str_hour + \":\" + str_min + \":\" + str_sec;
 ele_timer.value = time;
 n_sec++;
 if (n_sec > 59) {
 n_sec = 0;
 n_min++;
 }
 if (n_min > 59) {
 n_min = 0;
 n_hour++;
 }
 
 }, 1000);
 }
 
 
</ >