How to pass a variable from a Request as the return value of the global function js

Question

Hello and thank you in advance. I'm using npm tedious package to interact with a database. I'm also using Meteor.call and methods, for which I need to pass a variable (newdata in the example below) that carries the data taken from the database as the return value of the function "rr", so that I would be able to use the result of the function in the client by a Meteor call.

 function rr(){
        var newdata = [];

        var ahora = new Request("SELECT * FROM prueba", function (err) {
                if (err) {
                    console.log("err1");
                } else {
                }
            })
            ahora.on('row', function(columns) {
                columns.forEach(function(column) {
                    newdata.push(column.value);
                       });
                });
}

I want "newdata" to be the result of the rr function. How can I do that? If I write "return newdata" it's undefined, I can't use await because newdata is not the return value of any function...

Thank you very much.

Answer 1

Tedious doesn't seem to support promises natively, but you can wrap your function in a promise:

function rr() {
    return new Promise((resolve, reject) => {
        var ahora = new Request("SELECT * FROM prueba", function (err) {
            if (err) {
                reject(err);
            }
        });
        var newdata = [];
        ahora.on('row', function(columns) {
            columns.forEach(function(column) {
                newdata.push(column.value);
            });
        });
        resolve(newdata);
    }
}

Or slightly shorter:

function rr() {
    return new Promise((resolve, reject) => {
        new Request("SELECT * FROM prueba")
            .on("error", reject)
            .on("row", function(columns) {
                resolve(columns.map(column => column.value))
            });
    }
}

If you'd rather not make promises manually, you can try Bluebird's promisify function. I also found a tedious-specific promisifying package tedious-promises, but it doesn't seem to be properly maintained.