Mongoose, find, return specific properties - node.js

Question

I have this get call:
exports.getBIMFromProject = function(req, res){
mongoose.model('bim').find({projectId: req.params['prj_id']}, function(err, bim){
if(err){
console.error(err);
res.send(500)
}
res.send(200, bim);
});
};
Where do I specify which properties I want to return? Can't find it in the docs. The above returns the entire object. I only want a few properties returned.
This is my schema:
var mongoose = require('mongoose'),
Schema = mongoose.Schema;
var bimSchema = new Schema({
projectId: Number,
user: String,
items:[
{
bimObjectId: Number,
typeId: String,
position:{
floor: String,
room:{
name: String,
number: String
}
}
}
]
});
mongoose.model('bim', bimSchema);
I don't want the items array included in my rest call.

Answer 1

You use projection. The first example in the mongoose query docs has a projection operation tucked in.
NB: not real code b/c I highlighted the important bits with triple stars
// find each person with a last name matching 'Ghost', ***selecting the `name` and `occupation` fields***
Person.findOne({ 'name.last': 'Ghost' }, ***'name occupation'***, function (err, person) {
if (err) return handleError(err);
console.log('%s %s is a %s.', person.name.first, person.name.last, person.occupation) // Space Ghost is a talk show host.
})
The Person schema isn't specified but I think the example is clear enough.

Answer 2

Mongoose provides multiple ways to project documents with find, findOne, and findById.
1. Projection as String:
// INCLUDE SPECIFIC FIELDS
// find user and return only name and phone fields
User.findOne({ email: email }, 'name phone');
// EXCLUDE SPECIFIC FIELD
// find user and return all fields except password
User.findOne({ email: email }, '-password');
2. Projection by passing projection property:
// find user and return just _id field
User.findOne({ email: email }, {
projection: { _id: 1 }
});
3. Using .select method:
// find user and return just _id and name field
User.findOne({ email: email }).select('name');
// find user and return all fields except _id
User.findOne({ email: email }).select({ _id: 0 });
You can do the same with find and findById methods too.

Answer 3

MyModel.find({name: "john"}, 'name age address', function(err, docs) {
console.log(docs);
});
This will return fields - name, age and address only.

Answer 4

With the help of .select() this is possible.
If number of fields required are less from total fields then,
.select('projectId user') can be used
Else number of fields to be ignored are less from total fields then,
.select('-items') can be used.
So for getting a field, simply, space separated string of fields can be passed and for ignoring the field, space separated string with "-" before the field can be used.
For more documentation.

Answer 5

Find Specific properties also avoid some properties
await User.find({ email: email }, { name: 1, phone: 1, status: 1, password: 0 });

Answer 6

.Select() method is used to select which fields are to be returned in the query result
let result = await MyModel.find({ user : "user" }).select('name lastname status')