如何从mongoose中获取特定的不同字段？

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: String,
  age: Number,
  email: String
});

const User = mongoose.model('User', userSchema);

User.find({}, 'name email', function(err, users) {
  if (err) {
    console.error(err);
  } else {
    console.log(users);
  }
});

User.findOne({ name: 'John' }, 'name email', function(err, user) {
  if (err) {
    console.error(err);
  } else {
    console.log(user);
  }
});