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> npm install --save mongodb
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//mongodb 3以上写法
const MongoClient = require('mongodb').MongoClient;

//TodoApp是一个数据库名字，mongo中不需要创建数据库
MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');

  //插入数据
  db.collection('Todos').insertOne({
    text:'Something to do',
    completed:false
  },(err,result)=>{
    if(err){
        return console.log('unable to insert todo',err);
    }
        console.log(JSON.stringify(result.ops,undefined,2));
  });
//关闭客户端
  client.close();

});

id

插入一个对象的时候，会自动的产生一个随机的id。id包含了时间戳和机器识别码。
我们可以借助与mongo的方法，为我们产生一个随机数。

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const {MongoClient,ObjectID} = require('mongodb');
var obj = new ObjectID();
console.log(obj);
//返回时间
console.log(obj.getTimestamp());

参考资料：
MongoDB Node.js Driver Documentation
node-mongodb-native

查询

原始数据：

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[
  {
    "_id": "5bee9e3794c5f22eb989f6eb",
    "text": "Something to do",
    "completed": false
  },
  {
    "_id": "5beeaf0a2d48eb2b7c90758f",
    "text": "Something to do",
    "completed": true
  }
]

js代码：

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const {MongoClient,ObjectID} = require('mongodb');

MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');

  //返回所有document
  db.collection('Todos').find().toArray().then((docs)=>{
    console.log('Todos');
    console.log(JSON.stringify(docs,undefined,2));
  },(err)=>{
    console.log('unable to fetch todos', err);
  })

  client.close();
});

执行代码返回：

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[
  {
    "_id": "5bee9e3794c5f22eb989f6eb",
    "text": "Something to do",
    "completed": false
  },
  {
    "_id": "5beeaf0a2d48eb2b7c90758f",
    "text": "Something to do",
    "completed": true
  }
]

筛选

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const {MongoClient,ObjectID} = require('mongodb');

MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');
  db.collection('Todos').find({completed:true}).toArray().then((docs)=>{
    console.log('Todos');
    console.log(JSON.stringify(docs,undefined,2));
  },(err)=>{
    console.log('unable to fetch todos', err);
  })

  client.close();

});

执行代码返回：

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[
  {
    "_id": "5beeaf0a2d48eb2b7c90758f",
    "text": "Something to do",
    "completed": true
  }
]
筛选id
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const {MongoClient,ObjectID} = require('mongodb');

MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');
  db.collection('Todos').find({
    new ObjectID('5beeaf0a2d48eb2b7c90758f')
  }).toArray().then((docs)=>{
    console.log('Todos');
    console.log(JSON.stringify(docs,undefined,2));
  },(err)=>{
    console.log('unable to fetch todos', err);
  })

  client.close();

});

执行代码返回：

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[
  {
    "_id": "5beeaf0a2d48eb2b7c90758f",
    "text": "Something to do",
    "completed": true
  }
]

删除document

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const {MongoClient,ObjectID} = require('mongodb');

MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');
//  db.collection('Todos').deleteMany({text:'mike'});  删除全部

//删除一个
  // db.collection('Todos').deleteOne({text:'mike'}).then((result)=>{
  //     console.log(result);
  // });

//删除并返回对象
  db.collection('Todos').findOneAndDelete({text:'mike'}).then((result)=>{
      console.log(result);
  });

  client.close();

});

更新

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const {MongoClient,ObjectID} = require('mongodb');

MongoClient.connect('mongodb://localhost:27017/TodoApp',(err,client)=>{
    if(err){
      return console.log('Unable to connect to MongoDB server');
    }
    console.log('Connect to MongoDB server');
  const db = client.db('TodoApp');

//查找并更新
  db.collection('Todos').findOneAndUpdate({text:'mike'},{
    $set:{
      completed:false       //设置更改
    }
  },{
    returnOriginal:false  //返回的结果为更新后的值。
  }).then((result)=>{
    console.log(result); //打印跟新结果
  });

  client.close();
});

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