MongoDB How to catch errors in deleteMany - node.js

Question

I have looked at MongoDB documentation for deleteMany() but it seems the only error it throws is WriteConcernError.
I am using Insomnia to make my requests.
Here is my request:
DELETE HTTP://localhost:5000/api/users/delete/usernames?usernames=["a","b","c"]
As you can see I have an array in query string
so I pass that to my function
# user.controller.js
function _deleteByUsernames(req, res, next) {
userService.deleteByUsernames(JSON.parse(req.query.usernames))
.then(() => res.status(200).json({"message": "User(s) successfully deleted!"}))
.catch(err => next(err));
}
# user.service.js
async function _deleteByUsernames(usernames) {
try {
console.log(usernames);
await User.deleteMany({username: {$in: usernames}});
} catch (err) {
throw err;
}
}
I know there no documents with usernames a, b and c
but deleteMany() doesn't return any error something like "Coulnd't find given parameter" etc.
because I don't want to response with "User(s) successfully deleted".
How can I catch that error if there is one.
Or How should I handle that?

Answer 1

You may change your functions to below,
# user.controller.js:
put async/await in function, and add code in try/catch block, and pass res as param in service function deleteByUsernames,
async function _deleteByUsernames(req, res, next) {
try {
await userService.deleteByUsernames(res, JSON.parse(req.query.usernames));
} catch (err) {
next(err);
}
}
# user.service.js:
deleteMany(), This function calls the MongoDB driver's Collection#deleteMany() function. The returned promise resolves to an object that contains 3 properties:
ok: 1 if no errors occurred
deletedCount: the number of documents deleted
n: the number of documents deleted. Equal to deletedCount.
async function _deleteByUsernames(res, usernames) {
let response = await User.deleteMany({ username: { $in: usernames } });
// ERROR
if (response.ok != 1) {
res.status(400).json({ "message": "User(s) not deleted, Something want wrong!" });
}
// SUCCESS
else {
res.status(200).json({
"message": `${response.deletedCount} User(s) successfully deleted out of ${response.n}"
});
}
}
Code is not tested, you can workaround and see what happens!

Answer 2

I think there is no error for no found parameters.
I don't know this is better than nothing for now.
I am not going to mark this as answered because I don't think this is the answer
async function _deleteByUsernames(usernames) {
return await User.deleteMany({username: {$in: usernames}})
.then(result => {
console.log(result);
return (result.deletedCount === 0 ?
"None of the selected user(s) deleted!":
(result.deletedCount !== usernames.length ?
`${result.deletedCount} out of ${usernames.length} selected user(s) successfully deleted!`:
"All selected user(s) successfully deleted!"))
})
.catch(err => {
return `Delete failed with error: ${err}`;
})
}

Answer 3

You can save your delete result in a variable and check for the error
async function _deleteByUsernames(usernames) {
try {
console.log(usernames);
let userDeleteResult = await User.deleteMany({username: {$in: usernames}});
if(!userDeleteResult ){
res.json({status: false, error: 'Some error'}) // or pass the error object here
}
} catch (err) {
throw err;
}
}