Wait for function to complete in Nodejs - node.js

Question

I am trying to call a function inside my post API. I have multiple queries and want to wait for the function to complete in order to execute the next queries. I am having an issue here. The function isn't completing the execution and the rest of the API gets executed as expected. How can I wait for the function to complete its execution? I have searched but couldn't find something convenient and related to my code.
Here's the code:
Node.js
function verifyEmail(mailToUpper)
{
var emailResult;
db2.open(mydbConnection, (err, conn) => {
if(!err)
{
console.log("Connected Successfully");
}
else
{
console.log("Error occurred while connecting to the database " + err.message);
}
conn.query(checkEmailQuery, [mailToUpper], (err, results) => {
if(!err)
{
if(results.length > 0)
{
// res.write("Email already exists");
emailResult = 0;
}
else
{
emailResult = 1;
}
}
conn.close((err) => {
if(!err)
{
console.log("Connection closed with the database");
}
else
{
console.log("Error occurred while trying to close the connection with the database " +
err.message);
}
})
})
})
return emailResult;
}
router.post('/api/postData', (req, res) => {
//some stuff
var waitingForResult;
setTimeout(() => {
waitingForResult = verifyEmail(mailToUpper);
}, 2000)
console.log(waitingForResult); //throwing an error of undefined
if(waitingForResult === 1) //not executing this
{
//my other queries
}
else //always executes this
{
res.send("Email already exists");
}
});

Answer 1

function verifyEmail(mailToUpper) {
return new Promise((resolve, reject) => {
db2.open(mydbConnection, (err, conn) => {
if (!err) {
console.log("Connected Successfully");
} else {
console.log("Error occurred while connecting to the database " + err.message);
}
conn.query(checkEmailQuery, [mailToUpper], (err, results) => {
if (!err) {
if (results.length > 0) {
// res.write("Email already exists");
resolve(0);
} else {
resolve(1);
}
}
conn.close((err) => {
if (!err) {
console.log("Connection closed with the database");
} else {
console.log("Error occurred while trying to close the connection with the database " +
err.message);
}
})
})
})
})
}
router.post('/api/postData', async (req, res) => {
const waitingForResult = await verifyEmail( mailToUpper );
if( waitingForResult === 1 ){
//my other queries
} else {
res.send("Email already exists");
}
});