I have put the remaining timer on the exam page in an online examination system project which is fetching from the database. However, when I refresh it, the timer starts all over again. I want the timer, which has started, not to start again after a refresh and when the time is up, and the paper to be submitted automatically. Below, I have explained my code.

<form name="cd">
    <input type="hidden" name="" id="timeExamLimit" value="<?php echo $selExamTimeLimit; ?>">
    <label>Remaining Time : </label>
    <input style="border:none;background-color: transparent;color:blue;font-size: 25px;" name="disp" type="text"
           class="clock" id="txt" value="00:00" size="5" readonly="true"/>
</form>

//jQuery page
// Select Time Limit


var mins
var secs;

function cd() {
  var timeExamLimit = $('#timeExamLimit').val();
  mins = 1 * m("" + timeExamLimit); // change minutes here
  secs = 0 + s(":01"); 
  redo();
}

function m(obj) {
  for(var i = 0; i < obj.length; i++) {
      if(obj.substring(i, i + 1) == ":")
      break;
  }
  return(obj.substring(0, i));
}

function s(obj) {
  for(var i = 0; i < obj.length; i++) {
      if(obj.substring(i, i + 1) == ":")
      break;
  }
  return(obj.substring(i + 1, obj.length));
}

function dis(mins,secs) {
  var disp;
  if(mins <= 9) {
      disp = " 0";
  } else {
      disp = " ";
  }
  disp += mins + ":";
  if(secs <= 9) {
      disp += "0" + secs;
  } else {
      disp += secs;
  }
  return(disp);
}

function redo() {
  secs--;
  if(secs == -1) {
      secs = 59;
      mins--;
  }
  document.cd.disp.value = dis(mins,secs); 
  if((mins == 0) && (secs == 0)) {
    $('#examAction').val("autoSubmit");
     $('#submitAnswerFrm').submit();
  } else {
    cd = setTimeout("redo()",1000);
  }
}

function init() {
  cd();
}
window.onload = init;