Mongoose connection to Mongo DB: Best practice for exception cases - node.js

Question

It's not clear how to best trap errors using "mongoose.createConnection"
The Mogoose docs are pretty good at explaining how to trap an initial connection error when using "mongoose.connect" ... excerpt from docs., below:
mongoose.connect('mongodb://localhost:27017/test').
catch(error => handleError(error));
// Or:
try {
await mongoose.connect('mongodb://localhost:27017/test');
} catch (error) {
handleError(error);
}
However, in the case of "mongoose.createConnection" (neeed for more than one DB) ... this strategy does not seem to work. Here is what I've tried
const Db = mongoose.createConnection(dbUrl);
try {
await Db;
} catch (error) {
console.log(Error Connecting to DB");
}
which results in:
"SyntaxError: await is only valid in async functions and the top level bodies of modules"
Any pointers, please?
Thanks,
Tim.
Update following Anshu's post:
After making the changes, per Anshu, I then called the function
connectFunction()
and everything seemed OK, but only until the code reached the following line:
const Data = Db.model(`someCollection`, someSchema);
where it complained that "Db" is not defined. Presumably, because it is only scoped within the function? It feels like a chicken and egg situation. Any further guidance, please?
Update 11/18/22:
After making the following change:
async function connectFunction(){
try {
var db = await mongoose.createConnection(dbUrl);
} catch (error) {
console.log(Error Connecting to DB");
}
... same issue. I'm using VS Code and as a trivial observation, it colorizes variables, etc. In this case the variable "db" is "grayed out", i.e. it has recognized that something is wrong.
Update#2 11/18/22: I was able to make the "db is not defined error" go away once I realized I needed a return in the function. This is the latest code:
async function connectToBrandDb(url) {
try {
var Db = await mongoose.createConnection(url, {
keepAlive: true,
keepAliveInitialDelay: 300000,
serverSelectionTimeoutMS: 5000 });
}
catch (error) {
console.log(`Error Connecting To DB`);
}
return Db;
}
const brandDb = connectToBrandDb(dbUrl);
var Data = brandDb.model(`someCollection`, someSchema);
... and now looking at this from the terminal:
var Data = brandDb.model(`someCollection`, someSchema);
^
TypeError: brandDb.model is not a function

Answer 1

You should use async keyword before functions when you're trying to use await inside them. You cannot use await at the top (outside async function), so that's what the error is telling.
async function connectFunction() {
try {
const db = await mongoose.createConnection(dbUrl);
} catch (error) {
console.log("Error Connecting to DB");
}
}