你的后模式看起来很奇怪。 这有什么意义? post集合已经是posts的“数组”。

// Perhaps you are looking for something like this.
const PostSchema = new mongoose.Schema({
    title: String,
    content: String,
    level: Number,
    footer: String,
    author: ObjectId,// who wrote the post
    comments: [{
       user: ObjectId,
       comment: String
    }],
    ... createdAt, updatedAt etc
});

例如 等待Post.create({posts:req.body});