var adduser = function (user, pwd, callback) {
    var userid;
    client.incr("userid", function (err, reply) {
        userid = reply.toString();
    });
    client.lpush("user_id", userid, function (err, reply) {
        if (!err) {
            client.set("user_name_" + userid, user);
            clinet.set("user_pwd_" + userid, pwd);
            
        }
    });
}

注册用户这样写对不对？ 但是如果判断用户是否重复怎么写？

是不是这样写？

var adduser = function (user, pwd, callback) {
    client.get("user_" + user, function (reply) {
        if (reply == null) {//这里判断
            var userid;
            client.incr("userid", function (err, reply) {
                userid = reply.toString();
            });
            client.lpush("user_id", userid, function (err, reply) {
                if (!err) {
                    client.set("user_name_" + userid, user);
                    clinet.set("user_pwd_" + userid, pwd);
                    client.set("user_" + user, userid);//这里一加行
                    callback("注册成功");
                }
            });
        }
        else {
            callback("用户已存在");
        }
    });
    client.end();

}