Mongodb return array of strings instead array of objects
There is a way to select only tokens that require less processing using the mongodb aggregation framework
UserMdl.aggregate( { $match: { token : { $exists : true }}}, { $project: { _id: 0, token: 1 }}, function onUsersFound(err, tokens) { console.log(tokens); }););
This constructs an aggregation pipeline that first matches all documents that have a token field and then selects the token field and suppresses _id selection by using _id : 0
in the $project
pipeline step.
The post processing step would look like this:
function postProcess(tokenObjects) { if (!tokenObjects) { return []; } return tokenObjects.map(function(tokenObject) { return tokenObject.token; }); }
See also the mongoose docs for more detail on the aggregation function.
You don't need to do anything special. Just change one thing in your code:
Your code
UserMdl.find().exists('token').select('token').exec(function onUsersFound(err, userMdls) { console.log(userMdls); // (*) Change this to...});
Change
UserMdl.find().exec((err, users) => { console.log(users.map(user => user.token)); // ...(*) to this});
No need to use select
& exists
functions
EDIT
The best option is Mongoose distinct function:
const tokens = await UserMdl.distinct('token');
If you want condition then:
const tokens = await UserMdl.find(/* condition */).distinct('token');
Thats it