最简单的mongodb插入语句报错，求助求助！！！！

代码如下，这么简单的插入操作一直报错，而下面的查询操作则没有任何问题，错误信息见下图，跪求！

var mongo = require('mongodb'),
  Server = mongo.Server,
  Db = mongo.Db;

var server = new Server('localhost', 27017, {auto_reconnect: true});
var db = new Db('spa', server);

db.open(function(err, db) {
  if(!err) {
    console.log("We are connected");
  }
});

db.collection('spa', function(err, collection) {

    var doc1 = {a: 1};

    collection.insert(doc1, {safe:true}, function(err, result) {
        if(err){ throw err; };
        console.log(result.ok);
    });
});

db.collection('spa', function(err, collection){
    collection.find().toArray(function(error, result){
        if(error){ throw error; };
        console.log(result);
    });
});

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我换了一种方式，结果可以了，如下

var MongoClient = require('mongodb').MongoClient;  
    var url = 'mongodb://127.0.0.1:27017/spa';  
    MongoClient.connect(url, function(err, db) {  
        if (err)  {  
            console.log(err);  
        }else{  
            console.log("connect success!");  
        }  
    
        var col = db.collection("spa");  
    
        var data = {
            name:"gao qiang", 
            createTime:new Date().getTime(), 
            version:0
        };  
        
        col.save(data, [], function(err, result){  
            if(err){ throw err; };
            console.log(result);
        });  
    
        var cond = {};  //条件  
        var cols = {};  //要选择的列  
        var cursor = col.find(cond, cols, []);  
        cursor.toArray(function(err, result){  
            if(err){ throw err; };
            console.log(result);  
        });  
    }); 

---

mongodb 服务器版本多少