I'm trying to return a value after a for loop has been completed, the for loop is inside an async function. Inside the loop, there's a query that inserts to the db.

The function is working ok, but when i use postman, the response returns empty (even tho the values have been inserted to the db)

Here's how i call the function:

        insertarPracticas(turno_id,req.body.lista_codigos_practicas, queryInsertarPracticas)
        .then( result=> {
                 res.status(200).json({
                      "Practicas Agregadas": result
                    })
                 }
        )

And here's the function:

async function insertarPracticas(turno_id, req, queryInsertarPracticas){
//practicasAgregadas="";
return new Promise((resolve, reject) => {
    for (let i=0; i< req.length; i  ){ 
        connection.query(
            queryInsertarPracticas, [turno_id, req[i]],(error2, row2) => { 
                if (error2) {
                    console.log("Error al insertar turno detalle (prácticas): " req[i]  " "  error2);             
                    practicasNoAgregadas  = req[i]   "-";                   
                }else{
                    console.log("Turnos detalle agregados " req[i]);
                    practicasAgregadas  = req[i]   "-"; 
                    console.log("practicas " practicasAgregadas);
                }
        });
        console.log("en for " practicasAgregadas);
    }
    resolve(practicasAgregadas)

    // Or of there was an error
    reject("error");
})

What's happening here is that the function won't wait for the connection query to end, even tho it inserts values to the db, on Postman i get the first result, which is empty:

But i do have the values inserted on my database.

What's the correct way to handle this? I've tried using map instead of for, and now i'm trying with promise, but i'm not sure i'm using it correctly.

Here's the console, where you can see that the console.log("en for" practicasAgregadas) returns empty, when it should have some values.

CodePudding user response：

I don't know how you built your connection file, but you should change it to an async function and await the connection.query

CodePudding user response：

after your map, just use:

await Promise.all(yourArray);