MongoDB Find object within array

Question

I'm trying to find if a Username exists within my account collection. One account can have multiple users, but I'm trying to check if the username exists before I create an object with that username and return it if it does.

For now, I'm focusing on simply checking if it does exist. This is what I currently have:

const acc = await Account.findOne({"Email": req.body.Email});
if(!acc) throw Error('Email not found');
if(Account.findOne({"Users.Username":req.body.User.Username})) throw Error('Username already exists');

Edit: Not sure if this will help, but it's throwing the error, even when the User array is empty

I couldn't understand what's the problem in this explanation , Could you make your question more clarify and where is await for the second query ? — Momo
– Momo, Commented Mar 20, 2021 at 18:07
@MohammadMomeni Yeah, that await was the issue. I was trying to check if there was an object with an identical property value. It wasn't best explained, I admit — FallingInForward
– FallingInForward, Commented Mar 20, 2021 at 18:18

codemonkey · Accepted Answer · 2021-03-20 18:16:32Z

1

This statement:

Account.findOne({"Users.Username":req.body.User.Username})

will return a promise, which, regardless of what it will ultimately resolve to, will evaluate to true here if(Account.findOne({"Users.Username":req.body.User.Username})). So it's really no wonder your code throws that Username already exists error every time you run it.

You should change it to look what your first find looks like (i.e using await), or do something like this:

Account.findOne({"Users.Username":req.body.User.Username})
   .then(result => {
      if(result)
         throw Error('Username already exists');
      else
        ...
   })
   .catch(e => {...})

answered Mar 20, 2021 at 18:16

codemonkey

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6 Comments

FallingInForward Over a year ago

Yeah, that added await seemed to have been the issue. Thank you

FallingInForward Over a year ago

How would I set the User that is found to a variable?

codemonkey Over a year ago

@FallingInForward The same way you do it with the first await: const user = await Account.findOne({"Users.Username":req.body.User.Username}). Or using the promise structure I showed in the answer.

FallingInForward Over a year ago

That returns the entire account document. Users are an array of documents that is stored in each account

codemonkey Over a year ago

@FallingInForward If you show me a sample doc, I can show you how to retrieve the specific user from that array.

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