Fill array of objects with data from multiple mysql querys - mysql

Question

Is there a way to pause iteration of map function so I can get response from my query and store it in some object.
So my data is an array of objects and I want to add property "receivers" for every single object in array so I use map funtion to loop through my array, problem is in callback :D ,my object reveive data after my express sends response so I had to dely response with Timeout, I know its not the right solution but it work for now because I have only 40-50 records in database.
Here is the code:
data.map((x) => {
let sql = `
SELECT username
FROM message
JOIN message2user ON message.message_id = message2user.message_id
JOIN user on message2user.receiver_id = user.user_id
where message.message_id = ?;
`;
testDB.query(sql, x.message_id, (err, dataReceivers) => {
if (err) console.log(err);
x["receivers"] = dataReceivers;
})
});
setTimeout(() => {
res.json({ success: true, data: data });
}, 1000);
I am using express for my API routes and MySQL module for node, maybe I sould use Promises or async functions from node, I dont know.
Do you have any ideas??

Answer 1

Here's an approach using Promises if you don't want to refactor your SQL query:
const sqlTemplateString = `
SELECT username
FROM message
JOIN message2user ON message.message_id = message2user.message_id
JOIN user on message2user.receiver_id = user.user_id
where message.message_id = ?;
`;
Promise.all(data.map((x) => new Promise((resolve, reject) => {
testDB.query(sqlTemplateString, x.message_id, (err, dataReceivers) => {
if (err) {
reject(err);
} else {
x.receivers = dataReceivers;
resolve(x);
}
});
}))).then((data) => {
res.json({
success: true,
data
});
}).catch((error) => {
console.log(error);
res.json({
success: false,
error
});
});
Or something like that.