MongoDB & Node : $in with an ObjectId array

Question

I need to get a bunch of records from a collection based on their Ids. This is my function:

const getClassesForIDs = (classIDArray) => {
   
    console.log('in model getClassesForIDs');
    
    return new Promise((resolve, reject) => {
        
        Class.aggregate([
            {
                $match: {_id:{$in:classIDArray.map(_post => {new mongoose.Types.ObjectId(_post)})}}
            },
        ]).exec(function (err, classData) {
            if (err) {
                reject(err);
            } else {
                resolve(classData);
            }
        })
    })
}

classIdArray = ["6091468e749cd2f796f01efd", "60923c997b4d3205009a981b"]

Even though there are records matching these Ids, this function returns an empty array. When I run it in MongoDB compass, it returns the correct record:

{
  "_id" : {$in: [ObjectId('6091468e749cd2f796f01efd'), ObjectId('60923c997b4d3205009a981b')]}
}

What am I missing?

turivishal · Accepted Answer · 2021-05-06 05:40:16Z

3

The issues is in map function, correct this as below,

Remove bracket {} from map function or return the element through return keyword when you use {} bracket,

First syntax:

classIDArray.map(_post => new mongoose.Types.ObjectId(_post))

Second syntax:

classIDArray.map(_post => { return new mongoose.Types.ObjectId(_post) })

answered May 6, 2021 at 5:40

turivishal

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