How do we retrieve a Boolean with exists in mongoose?

Question

I am trying to check weather an account associated with the same username already exists or not. I am using the exist method to check but I keep getting a large object instead of a Boolean value.

async checkExisting(username,userCollection) { //WORK ON ISSUE WITH VERIFYING
        const check = new Promise((resolve,reject) => {
            let value = userCollection.exists({username})
            console.log(value);
            // if(userCollection.exists({username})) {
            //     reject("Username taken")
            // }

            resolve("Username avaliable")
        })

        return check;
    },

Please show us the value of the "*large object*" that you printed. It should be pretty clear what it represents and where the mistake is. — Bergi, Jan 02 '23 at 02:57

score 1 · Answer 1 · edited Jan 02 '23 at 17:02

Your code is correct. It's just what you write in resolve is returned. And no need to make the function async as you're already returning a Promise. So where you call this function there just keep await as follows

await checkExisting('username', 'collection')

checkExisting(username, userCollection)
{
 return new Promise((resolve, reject) => {
  userCollection
   .exists({username})
   .then((value) => {
    if (value) {
     resolve(true)
    }
    resolve(false)
   })
   .catch((err) => reject(err))
 })
}

Note: You can use either promise or async-await syntax; both ways are correct. However, never combine these two concepts as it will give unexpected output.

score 0 · Answer 2 · answered Jan 02 '23 at 03:00

userCollection.exists({username}) returns a query that you never ran. You need to actually execute it and wait for the result. Also avoid the Promise constructor antipattern. Just do

async checkExisting(username,userCollection) {
    const check = await userCollection.exists({username})
    if (check) {
        throw new Error("Username taken");
    }
    return "Username avaliable";
},

How do we retrieve a Boolean with exists in mongoose?

2 Answers2