下面的代码是我在Youtube视频中找到的一个4年前的例子。

TypeError: Cannot read properties of undefined (reading 'push')

有人能弄清楚新语法是什么吗？

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/test');
const Schema = mongoose.Schema;

const commentSchema = new Schema({
  text: String,
  username: String,
});

const postSchema = new Schema({
  text: String,
  username: String,
  comments: [commentSchema],
});

const PostModel = mongoose.model('post_coll', postSchema);
const CommentModel = mongoose.model('comment_coll', commentSchema);

const aPost = new PostModel({
  text: 'one',
  username: 'two',
});

aPost.comment.push({
  text: 'one',
  username: 'two',
});

aPost.save((err, res) => {});