NodeJS Returning 'undefined' In MySQL Query Function

Question

I have a function that queries SQL to get a string called Prefix.

function getPrefix(Guild) {
    let query = "SELECT Prefix FROM Guilds WHERE GuildId=?";
    Connection.query(query, [Guild.id], (err, result) => {
        if (err) throw err;
        return result[0].GuildPrefix;
    });
};

Whenever I print the Prefix out (console.log(result[0].Prefix);), it logs it fine - however, whenever I return it and then attempt to call the function, it always returns undefined.

I am using Node JS Version 10.15.1 & I am using MariaDB Version 10.1.37 on the Raspbian stretch of Debian. Please comment if I have left any other information out. Thanks.

Possible duplicate of https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call — vsemozhebuty, Feb 09 '19 at 19:41
Whenever you pass a callback function, it's always asynchronous — Patrick Hund, Feb 09 '19 at 20:00
Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Patrick Hund, Feb 09 '19 at 20:00

score 0 · Answer 1 · answered Nov 08 '20 at 08:47

In Nodejs the functions related to mysql are always asynchronous which means they will either not return anything or will retuen undefined.

So the solution is to use a callback function.
Eg.

function getPrefix(Guild, callback) {
    let query = "SELECT Prefix FROM Guilds WHERE GuildId=?";
    Connection.query(query, [Guild.id], (err, result) => {
        if (err){
         callback(JSON.stringify(err));
        };
        callback(JSON.stringify(result));
    });
};

NodeJS Returning 'undefined' In MySQL Query Function

1 Answers1