JavaScript timer is resetting while refreshing the page - timer

Question

I got a count down timer script.. I'm going to use it for a online examination.. But now the problem is it is resetting while refreshing the page...
Any idea to prevent the resetting the time and continue without any problem if they refresh the page too?
here is the code
<script>
var mins;
var secs;
function cd() {
mins = 1 * m("2"); // change minutes here
secs = 0 + s(":01"); // change seconds here (always add an additional second to your total)
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.getElementById("disp").innerHTML=dis(mins,secs); // setup additional displays here.
if((mins == 0) && (secs == 0)) {
window.alert("Time is up. Press OK to continue."); // change timeout message as required
// window.location = "yourpage.htm" // redirects to specified page once timer ends and ok button is pressed
} else {
cd = setTimeout("redo()",1000);
}
}
function init() {
cd();
}
window.onload = init;
</script>

Answer 1

If the page is refreshed, all you javascript code is re-executed. This is normal behaviour.
If you absolutely need to continue where you left, you can use the local storage API (only available in modern browsers) to store the time (every second you update the value).
When the page is loaded, you can then check if the value exists in Local storage, and start from where you were.
Are you sure you need this behaviour BTW?