Better way to find multiple collections with Mongoose for one render - node.js

Question

I am in the process of learning Node, Express and Mongoose and creating a web application. Sometimes, in one page, I need to display data from two or more of my collections. Although it works just fine, right now I use a bunch of nested if statements and have realized that the code has become very messy looking.
Example:
app.get("/jobs/:id/edit", function(req, res){
Job.findById(req.params.id, function(err, foundJob){
if (err){
console.log(err)
} else {
User.find({}, function(err, users){
if(err){
console.log(err);
} else {
Client.find({}, function(err, clients){
if(err) {
console.log(err);
} else {
let start_date = foundJob.start_date;
let end_date = foundJob.end_date;
start_date = moment(start_date).format("MM-DD-YYYY");
end_date = moment(end_date).format("MM-DD-YYYY");
// Redirect
res.render("edit_job", {job: foundJob, users: users, clients: clients, start_date, end_date});
}
});
}
});
}
});
});
This example is for a page that displays information from just three collections. Is there a better way to write this kind of code? I feel like using a table of collection names and using a for loop might work, but I am unsure how I would write that.
As an update, I tried the following logic, but it did not work:
app.get("/", function(req, res){
let collections = [Client, User, Ticket, Job];
let endCollections = [];
for (let i = 0; i < collections.length; i++){
collections[i].find({}, function(err, foundCollection){
if (err) {
console.log(err);
} else {
endCollections[i] = foundCollection;
}
})
}
res.render("dashboard", {clients: endCollections[0]});
No matter what I do, endCollections[i] remains undefined even though I have it set to be foundCollection, which is not undefined.
Thanks.

Answer 1

in the for-loop, you're executing an asynchronous block of code (collection.find()), so javaScript will not wait till this asynchronous code executed then do the next block of code which is the render, that's why you got an empty array
you need to use async/await to force javaScript to wait until the asynchronous block of code executed, then do the rest
just add async to the main function to be able to use await inside this function
something like this
app.get("/", async function(req, res){ // <== note the async keyword here
let collections = [Client, User, Ticket, Job];
let endCollections = [];
for (let i = 0; i < collections.length; i++){
await collections[i].find({}, function(err, foundCollection){ // <== note the await keyword here
if (err) {
console.log(err);
} else {
endCollections[i] = foundCollection;
}
})
}
res.render("dashboard", {clients: endCollections[0]});
hope it helps