expressjs - response body not set - node.js

Question

In the following NodeJS API, a PostgreSQL database is inserted with multiple rows and then a response body needs to be sent. Since there are multiple scenarios where there could be an error, I need to set-up response body with a message code that helps identify a possible cause. Therefore, I am using a resp object that will hold a code key for a message code. This object will be sent in a HTTP response where the status is either 200 (success) or 500 (error).
However, I keep getting an empty response body. Is the variable scope ok?
router.post('/', function (req, res, next) {
rdbmsPool.connect((err, client, release) => {
if (err) {
var resp = {
'Request-Id' : req.get('X-Request-Id'),
'code' : 'code'
}
res.status(500)
res.send(resp)
} else {
var resp = {}
for (k in someArray) {
client.query(queryString, colValues, (err, result) => {
if (err) {
resp = {
'Request-Id' : req.get('X-Request-Id'),
'code' : 'code'
}
res.status(500)
} else {
resp = {
'Request-Id' : req.get('X-Request-Id'),
'code' : 'code'
}
res.status(200)
}
})
}
for (k in someOtherArray) {
client.query(queryString, colValues, (err, result) => {
if (err) {
resp = {
'Request-Id' : req.get('X-Request-Id'),
'code' : 'code'
}
res.status(500)
} else {
resp = {
'Request-Id' : req.get('X-Request-Id'),
'code' : 'code'
}
res.status(200)
}
})
}
release()
res.send(resp)
}
})
});

Answer 1

Try something like this
let array1 = [];
for(k in someArray){
array1.push(client.query(queryString, colValues));
}
let array2 = [];
for (k in someOtherArray) {
array2.push(client.query(queryString, colValues));
}
try{
const results1 = await Promise.all(array1);
const results2 = await Promise.all(array2);
// if it comes here queries are successful
}
catch(error){
//send 500 here. any query have failed
console.log(error);
}

Answer 2

What happens is your response is sent before queries are completed. Your query execution is asynchronous and res.send(resp) does not wait until queries are executed.
The variable resp is set inside callbacks therefore it is empty.
You can try using async-await for synchronized execution with promise wrapper for parrelel execution of queries that are run inside loop. Note async function.
This is how it can be done with node mysql2/promise. Asynchronous means that the callback function you provide in query() will be called after query is executed. and the code after query() will run not waiting until query function is completed.
router.get('/getDayTypes',async function (req, res, next) {
const API_NAME='getDayTypes get, ';
try{
const conn = await pool.getConnection();
// Do something with the connection
var promise1 = conn.execute(`
SELECT
ID_DAY_TYPES,
DAY_NAME
FROM
hrm_calendar_day_types
WHERE
IS_ACTIVE = '1'`);
const values = await Promise.all([promise1]);
conn.release();
return res.status(200).send({success:true, data:values[0][0]});
}
catch(err){
logger.error(API_NAME + 'error :' + err);
return res.status(500).send({success:false, message:'Query Error'});
}
});