今天寫了這段用node.js驅動mongoDB訪問數據庫的代碼

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; }

調用方法為

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

在實際運行中，log的顯示結果為：

function2

finished
DB connected.

function1
DB connected.
DB authenticated.

DB connected.
DB authenticated.
data successfully written.
closed

也就是說，每次在數據庫函數中執行callback函數的時候，都會認為這個函數已經執行結束了，繼續執行該函數下面的語句，同時執行callback函數。

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轉載于:https://www.cnblogs.com/netaddi/p/5654580.html

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