// models/User.js const mongoose = require('mongoose'); const UserSchema = new mongoose.Schema({ username: { type: String, required: true, unique: true }, email: { type: String, required: true, unique: true }, password: { type: String, required: true }, }, { timestamps: true }); // timestamps会自动添加createdAt和updatedAt字段 module.exports = mongoose.model('User', UserSchema);