Inside foreach loop, the await is not working - asynchronous

Question

Below this code downloadcontroller.js
// Retrieve all downloads from the database.
exports.findAll = async (req, res) => {
downloadObj
.findAll(
{
include: [
{
model: composerObj,
required: false,
},
{
model: raagaObj,
required: false,
},
{
model: taalaObj,
required: false,
},
],
where: req.query,
raw:true,
nest: true,
})
.then((data) => {
data.forEach(async (element) => {
const artistsArray = [];
let whereConstraint = {};
JSON.parse(element.artists).forEach( async (ele) => {
artistsArray.push(ele.artistId);
});;
whereConstraint = {
id : {
[Op.in]: artistsArray
}
}
element.Active = "true11";
const artistData = artistService.customfindAll(whereConstraint);
element.artistData = artistData;
console.log("artistData",artistData);
});
console.log("data",data);
console.log("3");
res.status(200).send({
status:200,
message: "ok",
data:data
});
console.log("4");
})
.catch((err) => {
res.status(500).send({
status:500,
message:
err.message || "Some error occurred while retrieving Download.",
});
});
};
Below this code, artistServer.js file
exports.customfindAll = async (whereConstraint) => {
return new Promise(function(resolve, reject) {
artistObj
.findAll({
attributes:{
include: [
[fn('IF',literal('imagePath!=""'),(fn('CONCAT', artistImagePath, 'artist/', col('imagePath'))),artistImageDefaultPath), 'imageFullPath'],
],
},
where: whereConstraint,
order: [
['artistName', 'ASC'],
],
raw:true,
nest: true,
})
.then((data) => {
resolve(data);
});
});
}
Here my problem is
const artistData = artistService.customfindAll(whereConstraint);
not waiting for the data. .So that I got the result, below have mentioned. Actually the artistData attribute column, need result data.
{
"status": 200,
"message": "ok",
"data": [
{
"id": 1,
"fileType": "1",
"customFileName": "test filename",
"artists": "[{\"artistId\":1},{\"artistId\":4},{\"artistId\":2}]",
"accompanyingArtists": "[{\"instrumentId\":1,\"accompanyingArtistId\":1},{\"instrumentId\":2,\"accompanyingArtistId\":6},{\"instrumentId\":3,\"accompanyingArtistId\":4}]",
"Active": "true11",
"artistData": {}
},
{
"id": 2,
"fileType": "1",
"customFileName": "new file name",
"artists": "[{\"artistId\":1},{\"artistId\":4},{\"artistId\":2},{\"artistId\":6},{\"artistId\":3}]",
"accompanyingArtists": "[{\"instrumentId\":1,\"accompanyingArtistId\":1},{\"instrumentId\":2,\"accompanyingArtistId\":6},{\"instrumentId\":3,\"accompanyingArtistId\":4},{\"instrumentId\":3,\"accompanyingArtistId\":3},{\"instrumentId\":4,\"accompanyingArtistId\":2}]",
"Active": "true11",
"artistData": {}
}
]
}
In console page, I artistdata attribute pending...
enter image description here

Answer 1

The customFindAll function returns a Promise but the forEach does not wait for it. Add an await:
const artistData = await artistService.customfindAll(whereConstraint);
Also, forEach does not wait, it just fires off the async functions and move on. To wait for the forEach to finish, you need a map and a Promise.all, like this:
await Promise.all(data.map(async (element) => {
const artistsArray = [];
let whereConstraint = {};
JSON.parse(element.artists).forEach( async (ele) => {
artistsArray.push(ele.artistId);
});;
whereConstraint = {
id : {
[Op.in]: artistsArray
}
}
element.Active = "true11";
const artistData = await artistService.customfindAll(whereConstraint);
element.artistData = artistData;
console.log("artistData",artistData);
}));
The way it works this way is that data.forEach(async (e) => ... runs the async function and discards the results (the Promises). If you use a map, like data.map(async (e) => ..., you'll get an array of Promises, then use await Promise.all(...) to wait for them.