make a mongoose model add new item without removiing old one code example

Example 1: mongoose find by and delete

Campground.findByIdAndRemove(req.params.id, function(err){
      if(err){
          res.redirect("/campgrounds");
      } else {
          res.redirect("/campgrounds");
      }
   });

Example 2: mongoose model

const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = mongoose.model('Tank', schema);