Javascript get mongoose data inside an Async Array.prototype.map()

Question

I'm working on my nodejs project and I just noticed that waiting for mongoose queries inside an async .map() iteration returns null.

    const arr = [1, 2, 3, 4]
    const result = arr.map(async obj => {
        return {
            number: obj,
            user: await User.findOne({role: 'admin'})
        }
    })
    Promise.all(result).then(res => {
        console.log(result)
    })
    res.sendStatus(200)

log:

[
  Promise { { number: 1, user: null } },
  Promise { { number: 2, user: null } },
  Promise { { number: 3, user: null } },
  Promise { { number: 4, user: null } }
]

How can I get the data from mongoose inside an async Array.prototype.map() properly?

adhi narayan · Accepted Answer · 2020-05-13 17:48:13Z

1

const arr = [1, 2, 3, 4]
const result = arr.map(async obj => {
    return {
        number: obj,
        user: await User.findOne({role: 'admin'}).exec()
    }
})
Promise.all(result).then(res => {
    console.log(result)
})
res.sendStatus(200)

note the .exec() after findOne

answered May 13, 2020 at 17:48

adhi narayan

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1 Comment

EKnot Over a year ago

the output stays the same.

Alboman · Accepted Answer · 2020-05-13 18:08:00Z

0

I would probably add that if you are doing a findOne with a role admin mongo will probably return the same document all the time.

answered May 13, 2020 at 18:08

Alboman

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1 Comment

EKnot Over a year ago

Oh yes, but just made this up as an example.

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