example for get data from mongodb with mongoose in express app with pagination( without additional npm packages)

get_with_pagination.js

app.get('/:pageNum', function (req, res) {
  try {
    // how many to items to load everytime
    const perPage = 12;
    // which page is current?
    const page = req.params.pageNum || 1;
    // find all
    ClientModel.find({})
    // skip number of items (number of pages we passed * number of items per page) minus one of that number of 
    // items per page (to get the current one we get as param)
      .skip((perPage * page) - perPage)
    // limit number of items to fetch to be as defined from since started
      .limit(perPage)
      .exec(function (err, data) {
      // how many items we have? (gonna divide that amount over number of items per page
        ClientModel.count().exec(function (err, count) {
          if (err) {
            logger.error(`CRUD_CLIENT/GET_ALL error:${err}`);
            res.status(500)
              .json({ success: false, message: "Internal server error" });
          } else {
            res.status(200).json({
              success: true, message: "data loaded successfully", data: data, pages: {
                current: page,
                total: Math.ceil(count / perPage)
              }
            });
          }
        });
      });
  } catch (error) {
    logger.error(`CRUD_CLIENT/GET_ALL error:${err}`);
    next(error);
  }
});