点击获取验证码进行60秒倒计时

$(\'.getCode\').on(\'click\', function() {
            var self = $(this);
            countdown(self);
        });
        var countdownNum = 60;

        // 倒计时
        function countdown(obj) {
            if(countdownNum == 0) {
                obj.attr(\'disabled\', false); 
                obj.val(\'获取验证码\');
                countdownNum = 60;
                return;
            } else {
                obj.attr(\'disabled\', true);
                obj.val(countdownNum + \'秒后重新发送\');
                countdownNum--;
            }

            setTimeout(function () {
                countdown(obj);
            }, 1000);  
        }