why mongoose populate() request does not work? - mongodb

Question

I try to populate some data from other collection to an other collection.i had googled the search and also i follow the tutorial step by step but the population had fail.any help is appreciate friends. this is the code:
router.get("/", passport.authenticate("jwt", {session: false}), (req, res)=> {
const errors = {};
Profile.findOne({user: req.user.id})
.then(profile => {
if (!profile) {
errors.noprofile = "there is no profile for this user"
return res.status(404).json(errors);
}
res.json(profile);
}).catch(err=> res.status(404).json(err))
});
// #route POST api/profile
//#desc Create or edit user profile
//#access Private
router.get("/", passport.authenticate("jwt", {session: false}), (req, res)=> {
const {errors, isValid} = validateProfileInput(req.body);
//Check validation
if(!isValid) {
return res.status(400).json(errors);
}
// Get profile data
const profileData = {};
profileData.user = req.user.id;
if(req.body.handle) {
profileData.handle = req.body.handle
};
if(req.body.company) {
profileData.company = req.body.company
};
if(req.body.website) {
profileData.website = req.body.website
};
if(req.body.location) {
profileData.location = req.body.location
};
if(req.body.status) {
profileData.status = req.body.status
};
if(typeof req.body.skills !== 'undefined') {
profileData.skills = req.body.skills.split(',');
}
//social
profileData.social = {};
if(req.body.youtube) {
profileData.social.youtube = req.body.youtube
};
if(req.body.twitter) {
profileData.social.twitter = req.body.twitter
};
if(req.body.facebook) {
profileData.social.facebook = req.body.facebook
};
if(req.body.instagram) {
profileData.social.instagram = req.body.instagram
};
Profile.findOne({user: req.user.id})
.populate(
"user",
["name, avatar"]
)
this is the result that I get from the postman :
"_id": "62ee1058ceb295ccdfedffce",
"user": "62e6825958870d3db69d2da5",
"handle": "pablo",
"status": "developper",
"skills": [
"design web"
],
and the correct result must be :
"_id": "62ee1058ceb295ccdfedffce",
"user": {"_id": "62e6825958870d3db69d2da5",
"name": "pablo",
"avatar": "//www.gravatar.com/avatar/1ffsrenbdgeajks-ghsdereys1dkkdhddbc"
}
"handle": "pablo",
"status": "developper",
"skills": [
"design web"
],