NodeJS mysql 承诺返回未定义

Question

I'm trying to do command for discord bot that outputs integer from MySQL table.

I tried doing this with async/await, with promises, with callbacks but the result is always same. Here I'm trying it again with promises, because in past it somehow worked. Now it won't.

Here's function that returns promise:

exports.checkAccess = (user) => {
    return new Promise((resolve,reject) => {
        sql.condb.query("SELECT `accessLevel` FROM `users` WHERE `DiscordID` = '" + user + "' LIMIT 1", function(err,rows){
            if(err) reject(err);
            else resolve(rows);
        })
    });
}

And here's code that assigns result to accessLevel variable:

let accessLevel = -1;
cmds.checkAccess(message.author.id).then(rows=>{
        accessLevel = rows[0].accessLevel;
    }).catch((err)=>{
        console.log(err);
});

Catch function catches error that says "TypeError: Cannot read property 'accessLevel' of undefined".

Answer 1

It seems that your query does not return any results rather then undefined promise.

I suggest you to put your query into variable and use console.log to get generated query so that you can check your final query.

let query = "SELECT `accessLevel` FROM `users` WHERE `DiscordID` = '" + user + "' LIMIT 1";
console.log(query);

Try to select stdout query into your mysql editor.