JavaScript 判断 Undefined 类型

 var cookiestr = '';
     chrome.cookies.getAll(
         {
             'url': 'https://mp.weixin.qq.com',
             'secure': true
         }, function (cookies) {
             for (var i in cookies) {
                 if (typeof (i.name) != 'undefined' && typeof (i.value) != 'undefined') {
                     cookiestr += i.name + '=' + i.value + ';';
                 }
             }
             alert(cookiestr);

     });