JavaScript检测是否存在cookie

function checkCookie(){
    var user=getCookie("username");
    if (user!=""){
        return 1;
    }
    else {
        return 0;
    }
}//检测cookie是否存在
function getCookie(cname){
    var name = cname + "=";
    var ca = document.cookie.split(';');
    for(var i=0; i<ca.length; i++) {
        var c = ca[i].trim();
        if (c.indexOf(name)==0) { return c.substring(name.length,c.length); }
    }
    return "";
}

代码参考：https://www.runoob.com/php/php-cookies.html