如果未定义属性，请跳至else

我有创建团队并将数据放入数据库的功能。现在我正在尝试检查团队是否已经存在，如果确实存在，则回复消息。我的if语句有问题。

if（result [0] .teamname == teamName）

当结果[0] .teamname未定义时，它显示无法读取未定义的属性'teamname'它忽略其他并抛出错误。我该如何做到不忽视别的？

这是我用来创建团队的功能。

function createTeam(teamName, members, message) {
teamName = teamName.replace("_", " ");
let insertTeam = `INSERT INTO teams (teamname) VALUES ('${teamName}');`;

db.select(`SELECT id_t, teamname FROM teams WHERE teamname = '${teamName}'`, function(err, result) {
    if (err) {
        throw err;
    } else {
        if (result[0].teamname == teamName) {
            if (message.guild !== null) message.delete();

            message.reply("this team already exists!");
        } else {
            db.query(insertTeam);

            db.select(`SELECT id_t FROM teams WHERE teamname = '${teamName}'`, function(err, result) {
                if (err) {
                    throw err;
                } else {
                    for (let i = 0; i < members.length; i++) db.query(`INSERT INTO team_user (user, team) VALUES ('${members[i]}' , ${result[0].id_t})`);
                }
            });

            if (message.guild !== null) message.delete();

            let newTeam = new Discord.RichEmbed()
            .setThumbnail(".png?v=1")
            .setColor("#15f153")
            .addField("New team has been created!", `Team ${teamName} has been created with total of ${members.length} members!\nGood luck!`);

            message.channel.send(newTeam);
        }
    }
});

到目前为止我尝试了什么：

1. 检查result [0] .teamname是否未定义
2. 检查结果长度是否不为0
3. try-catch语句

if（result [0] && result [0] .teamname == teamName）

首先，您需要检查result [0]是否未定义