Returning boolean from postgresql pool - node.js

Question

I'm currently trying to validate username and password in a function that calls another function from postgresql. My validation should return true in the validate function but it doesn't. The console.log above it works and the parameters I use when I actually use validate() should return true but isn't.
function validate(username, password){
//PG Connect
pool.connect((err, client, done)=>{
if(err){
return console.error('error fetching client from pool', err);
}
client.query('SELECT * FROM users', (err, result)=>{
if(err){
return console.error('error running query', err);
}
for(let i = 0; i < result.rows.length; i++){
if(result.rows[i].username.trim() == username && result.rows[i].password.trim() == password){
console.log("this works");
return true; //this doesn't return true when I call the function
}
console.log(result.rows[i].username.trim() + " " + result.rows[i].password.trim());
}
return false;
done();
});
});
}

Answer 1

The problem is that you're returning within the query's callback instead of the parent function. This means validate() is actually not returning anything.
An easy solution to this would be to make use of either a Promise or a callback on validate. Here is how you could implement the Promise method...
function validate(username, password) {
return new Promise((resolve, reject) =>
pool.connect((err, client, done) => {
if (err) {
return reject(err);
}
client.query('', (err, results) => {
done();
if (err) {
return reject(err);
}
// logic here
resolve(false); // failed validation
});
});
});
}
And you would use it like so...
validate('username', 'password')
.then(valid => console.log(valid))
.catch(err => console.error(err));
Where all your reject() calls are caught in the catch and all the resolve() calls are caught in then.