Node Js asyncronic mysql query - mysql

Question

I´m trying to do an asynchronous query in NodeJS but keep getting undefined as a result, my code is:
async function Nuevo_Parametro() {
sqlStr = "select * from Parametros limit 10";
conCasos.query(sqlStr, function(err, Resultado, fields) {
if (err) throw err;
return Resultado;
});
}
Nuevo_Parametro().then(Resultado => {
console.log(Resultado);
});
What am I doing wrong?
Thanks in advance

Answer 1

you're mixing callback styles with Promises. The mysql function does not return a Promise, so you can't concatenate it. It uses a callback style - meaning the "async" part is executed in that callback you provide as a parameter.
What you need to do is wrap it up with a Promise and return that. Something along the lines of the following
function Nuevo_Parametro() {
sqlStr="select * from Parametros limit 10"
return new Promise((resolve, reject) => {
conCasos.query(sqlStr, function(err, Resultado,fields) {
if (err) {
return reject(err)
};
resolve(Resultado);
})
})
}
Nuevo_Parametro().then(Resultado => {
console.log(Resultado)
})
Here we return a promise we're creating, and in the callback query offers, I'm resolving it. I kept the variables and property names as they are for simplicity.
If you're going to use extensively the queries, perhaps it might be tedious to be newing promises everytime, so as it's mentioned in this github ticket you can use a wrapper like this one
or maybe use the native promisify utility as this comment states
const fn = util.promisify(connection.query).bind(connection);
const rows = await fn('SELECT col1, col2 FROM users WHERE email = ?', [email]);