关于node.js的思考

今天写了这段用node.js驱动mongoDB访问数据库的代码

function writeDB(receivedText, time, user) {var db_host = 'host';var port = 27017;var username = "usr";var pwd = "pwd";var db_name = "db";var result = "";var mongoClient = mongodb.MongoClient;mongoClient.connect(db_host, function (err, db) {if(err){console.log("error-1" + err);}result += "DB connected.\n";console.log(result);db.authenticate(username, pwd, function (err, res) {if(err){console.log("error0" + err);}result += "DB authenticated.\n";console.log(result);db.collection('note').insert({"text": receivedText,"time": time,"user": user}, function(err, res){if(err){console.log("error1" + err);}result += "data successfully written.";console.log(result);db.close();console.log("closed");return result;});});console.log("function1");});console.log("function2");return result; }

调用方法为

var dbResult = writeDB(receivedText, getTime(), "default user");console.log(dbResult);console.log("finished");res.send("succedded");

在实际运行中，log的显示结果为：

function2

finished
DB connected.

function1
DB connected.
DB authenticated.

DB connected.
DB authenticated.
data successfully written.
closed

也就是说，每次在数据库函数中执行callback函数的时候，都会认为这个函数已经执行结束了，继续执行该函数下面的语句，同时执行callback函数。

 

转载于:https://www.cnblogs.com/netaddi/p/5654580.html

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