启动mongoose

启动mongoose需要先安装mongoose模块，然后在代码中引入mongoose模块并连接数据库。以下是一个简单的示例代码：

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/my_database', { useNewUrlParser: true });

const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  console.log('Connected to database!');
});