一个简单的nodejs连接mongodb示例，来自 mongodb官方示例

1. 创建package.json

首先，创建我们的工程目录connect-mongodb，并作为我们的当前目录

mkdir connect-mongodb
cd connect-mongodb

输入npm init命令创建package.json

npm init

然后，安装mongodb的nodejs版本driver
npm install mongodb --save
mongodb驱动包将会安装到当前目录下的node_modules中

2. 启动MongoDB服务器

安装MongoDB并启动MongoDB数据库服务，可参考我之前的文章，或者MongoDB官方文档

3. 连接MongoDB

创建一个app.js文件，并添加以下代码来连接服务器地址为192.168.0.243，mongodb端口为27017上名称为myNewDatabase的数据库

var MongoClient = require('mongodb').MongoClient,
    assert = require('assert');

// Connection URL
var url = 'mongodb://192.168.0.243:27017/myNewDatabase';

MongoClient.connect(url,function(err,db){
    assert.equal(null,err);
    console.log("Connection successfully to server");
    db.close();
});

在命令行输入以下命令运行app.js
node app.js

4. 插入文档

在app.js中添加以下代码，使用insertMany方法添加3个文档到documents集合中

var insertDocuments = function(db, callback){
    // get ths documents collection
    var collection = db.collection('documents');

    // insert some documents
    collection.insertMany([
        {a:1},{a:2},{a:3}
    ],function(err,result){
        assert.equal(err,null);
        assert.equal(3,result.result.n);
        assert.equal(3,result.ops.length);
        console.log("Inserted 3 documents into the collection");
        callback(result);
    });
};

insert命令返回一个包含以下属性的对象:

• result MongoDB返回的文档结果
• ops 添加了_id字段的文档
• connection 执行插入操作所使用的connection

在app.js更新以下代码调用insertDocuments方法

var MongoClient = require('mongodb').MongoClient
  , assert = require('assert');

// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err);
  console.log("Connected successfully to server");

  insertDocuments(db, function() {
    db.close();
  });
});

在命令行中使用node app.js运行

5. 查询所有文档

添加findDocuments函数

var findDocuments = function(db,callback){
    // get the documents collection
    var collection = db.collection('documents');
    // find some documents
    collection.find({}).toArray(function(err,docs){
        assert.equal(err,null);
        console.log("Found the following records");
        console.log(docs);
        callback(docs);
    });
};

findDocuments函数查询了所有’documents’集合中所有的文档，将此函数添加到MongoClient.connect的回调函数中

var MongoClient = require('mongodb').MongoClient
  , assert = require('assert');

// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err);
  console.log("Connected correctly to server");

  insertDocuments(db, function() {
    findDocuments(db, function() {
      db.close();
    });
  });
});

6. 使用过滤条件(query filter)查询文档

查询’a’:3的文档

var findDocuments = function(db, callback) {
  // Get the documents collection
  var collection = db.collection('documents');
  // Find some documents
  collection.find({'a': 3}).toArray(function(err, docs) {
    assert.equal(err, null);
    console.log("Found the following records");
    console.log(docs);
    callback(docs);
  });      
}

7. 更新文档

var updateDocument = function(db,callback){
    // get the documents collection
    var collection = db.collection('documents');
    // update document where a is 2, set b equal to 1
    collection.updateOne({a:2},{
        $set:{b:1}
    },function(err,result){
        assert.equal(err,null);
        assert.equal(1,result.result.n);
        console.log("updated the document with the field a equal to 2");
        callback(result);
    });
};

updateDocument方法更新满足条件a为2的第一个文档，新增一个b属性，并将其设置为1。
将updateDocument方法添加到MongoClient.connect方法的回调中

MongoClient.connect(url,function(err,db){
    assert.equal(null,err);
    console.log("Connection successfully to server");
    insertDocuments(db,function(){
        updateDocument(db,function(){
            db.close();
        });
    });
});

8. 删除文档

var removeDocument = function(db,callback){
    // get the documents collection
    var collection = db.collection('documents');
    // remove some documents
    collection.deleteOne({a:3},function(err,result){
        assert.equal(err,null);
        assert.equal(1,result.result.n);
        console.log("removed the document with the field a equal to 3");
        callback(result);
    });
};

添加到app.js中

var MongoClient = require('mongodb').MongoClient
  , assert = require('assert');

// Connection URL
var url = 'mongodb://localhost:27017/myproject';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err);
  console.log("Connected successfully to server");

  insertDocuments(db, function() {
    updateDocument(db, function() {
      removeDocument(db, function() {
        db.close();
      });
    });
  });
});

9. 创建索引

索引能够改善应用的性能。下面你代码在’a’属性上添加索引

var indexCollection = function(db,callback){
    db.collection('documents').createIndex({
        a:1
    },null,function(err,results){
        console.log(results);
        callback();
    });
}; 

更新app.js

MongoClient.connect(url,function(err,db){
    assert.equal(null,err);
    console.log("Connection successfully to server");
    insertDocuments(db,function(){
        indexCollection(db,function(){
            db.close();
        });
    });
});

代码已经托管在码云