when I do the registration page and send the CAPTCHA countdown, I save the second seconds of the countdown as cookie, so that I can continue to execute the timer when I refresh and leave the page, instead of starting from the heart.
but when I use window.location.href to jump to the page and go back to the registration page, I find that the number of seconds is still the number of seconds I left the page

has anyone solved it?

//
$(".btnStr").click(function(){
    var second = 30;
    start(second);
})
function start(second){
    var timer = setInterval(function(){
        if(second>0){
            second--;
            $(".btnStr").html(second+"");
        }else{
            $(".btnStr").html("");
            clearInterval(timer);
        }
        setCookie("second",second,1);
    },1000)
}
//cookie
function setCookie(cname,cvalue,exdays){
    var d = new Date();
    d.setTime(d.getTime()+(exdays*24*60*60*1000));
    var expires = "expires="+d.toGMTString();
    document.cookie = cname+"="+cvalue+"; "+expires;
}
//cookie
function getCookie(cname){
    var name = cname + "=";
    var ca = document.cookie.split(";");
    for(var i=0; i<ca.length; iPP) {
        var c = ca[i].trim();
        if (c.indexOf(name)==0) { return c.substring(name.length,c.length); }
    }
    return "";
}
//cookie
function checkCookie(){
    var overplus=getCookie("second");
    if (overplus!=0){
        start(overplus);
    }
}