Getting results from the asynchronus query in nodejs

Question

I'm extracting some data from the database, to use it in my nodejs app. I'm using node-postgres to connect to the db ( https://node-postgres.com/ ).

I went through the guidance multiple times and tried querying it in different ways (callback, promise, using pool and client), but always get errors.

const { Pool } = require('pg');

const pool = new Pool({
  user: 'user',
  host: 'host',
  database: 'db',
  password: 'pass',
  port: port,
});

pool.query('SELECT * from table').then(res=> {
var projects = res.rows; 
console.log(projects); 
return projects;
});

//... few other operations on projects data to follow before exports

exports.raw = projects;

I can see the data in the console output, so the connection is working, but when I try to run the code I get

ReferenceError: projects is not defined.

Grateful for any help with this.

Answer 1

You can simply achieve by async/await code format

users.js

const users = {};

const { Pool } = require('pg');

const pool = new Pool({
  user: 'user',
  host: 'host',
  database: 'db',
  password: 'pass',
  port: process.env.port,
});

users.getUsers = async () => {
  try {
    const result = await pool.query('SELECT * FROM users');
    console.log(result);
    return result;
  } catch (err) {
    console.error(err);
    throw err;
  }
};

module.exports = users;

friends.js

const friends = {};

const users = require('./users');

friends.getSampleData = async () => {
  try {
    const result = await users.getUsers();
    console.log(result);
    return result;
  } catch (err) {
    console.error(err);
    throw err;
  }
};

module.exports = friends;

Note async/await only works on a function which returns a Promise .

Answer 2

Just like Jeremy answered, create a getter method in order to fetch data, don't try to store it before you need it.

const fetchData = async() => {
  const res = await pool.query('SELECT * from table')
  return res.rows;
}

const myDesiredData = fetchData()

Answer 3

Try the async/await syntax :

let projects;

(async () => {
    const res = await pool.query('SELECT * from table');
    projects = res.rows;
})();

exports.raw = projects;