NodeJS map() function return new object by doing some DB operation and return operation result

Question

I am working with node js/MongoDB to fetch all posts and checked whether the user already like or not for this particular post if liked then add a key "isLiked" in each object. But unable to do that.

Post.find().exec(function(err, posts) {
  if (err) {
    return res.status(500).json({ message: err.message });
  }

  var result = posts.map(isLiked(req.user));

  console.log(result);
  return res
    .status(200)
    .json({ message: "Successfully fetch all posts", result: result });
});

var isLiked = function(user) {
  return function(x) {
    var o = Object.assign({}, x);
    o.isLiked = Post.find(
      {
        _id: x._id,
        likes: user
      },
      function(err, isliked) {
        if (isliked != "") {
          return 1
        } else {
          return 0;
        }
      }
    );
    return o;
  };
};