javascript function will not return value or object

Question

Please help trying to get this function to return value back to my main process. currently everything shows in the console however if I return the object its blank or undefined

const GetSelectDeviceFromDB = () => {
  db.all("SELECT * FROM device_list", function (err, rows) {
    rows.forEach(function (row) {
      console.log(row.device);
      return row.device;
    });
  });
};

module.exports = { GetSelectDeviceFromDB };

OUPUTS:
console.log =. { device1, device2 }
return = undefined and if I add the return to the beginning of the sql statement I get {}

`forEach()` doesn't return anything. Use `map()` to return a list of the result of each function. — Barmar, Mar 01 '21 at 21:41
But `db.all()` is asynchronous. See https://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-asynchronous-call — Barmar, Mar 01 '21 at 21:42
Does this answer your question? [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) — Phix, Mar 01 '21 at 21:46

Dan Cantir · Accepted Answer · 2021-03-27T14:24:46.840

Since all() method is asynchronous and it is using a callback, you can turn your method into a method like this:

const GetSelectDeviceFromDB = () => new Promise((resolve, reject) => {
  db.all('SELECT * FROM device_list', (err, rows) => {
    if (err) {
      reject(err);
    }
    const devices = rows.map((row) => row.device);
    resolve(devices);
  });
});

It will return a Promise, so you can call it like this:

GetSelectDeviceFromDB().then(devices => { ... })

score 0 · Answer 2 · answered Mar 01 '21 at 21:49

Returning from forEach isn't a good idea, returning from another object's method (db.all in you case) isn't either. You need to return exactly in the first scope of the lambda function, somewhere outside of db.all(...). But in this case it's an async method, so you should make your whole function async or a Promise

javascript function will not return value or object

2 Answers2