express连接mongoDB实例

1.创建连接

// utils/mongoConfig.js

const mongoose = require('mongoose');

// 创建连接实例
const mongoUrl = 'mongodb://admin:123456@127.0.0.1:27017/express-test?authSource=admin';
mongoose.connect(mongoUrl, { useNewUrlParser: true, useUnifiedTopology: true  });

// 创建User集合连接
const UserSchema = mongoose.Schema({
  name: String,
  age: Number
});
const User = mongoose.model('User', UserSchema, 'user');


// 创建student集合连接
const StudentSchema = mongoose.Schema({
  name: String,
  grade: Number,
  class: String
});
const Student = mongoose.model('Student', StudentSchema, 'student');

module.exports = {
  User,
  Student
};

2.使用

// routers/index.js

router.get('/mongo', async (req, res) => {
  const result = await User.aggregate([
    {
      $lookup: {
        from: 'student',
        localField: 'name',
        foreignField: 'name',
        as: 'item'
      }
    },
    { $project: {'name':1,'age':1,'item.grade':1,'item.class':1} },
    {
      $group: { _id:"$item.class", count:{$sum: 1} }
    }
  ])
  res.send(result);
})