How To Return Value From Node.js Function Which Contains Db Query

I'm learning Node.js and I'm just starting to work with some MySQL connections. I have a function which is supposed to get a set of rows from the database, which it does correctly.

Solution 1:

You need to pass a callback into your function. Convention is that the callback takes an error (or null if none happened) as the first argument, and results as other arguments.

functionfetchGameList(callback) {
    var ret;

    connection.query("SELECT * from tbl", function(err, rows, fields) {
        if (err) {
            // You must `return` in this branch to avoid using callback twice.returncallback(err);
        }

        // Do something with `rows` and `fields` and assign a value to ret.callback(null, ret);
    });
}

You can now do something along the lines of:

function handleResult(err, result) {
    if (err) {
        // Just an example. You may want to do something with the error.
        console.error(err.stack || err.message);

        // You should return in this branch, since there is no result to use// later and that could cause an exception.
        return;
    }

    // All your logic with the result.
}

fetchGameList(handleResult);