为什么我的async.waterfall JavaScript时序代码没有结束？

Question

当我运行下面的代码，它顺序连接到MongoDB，然后关闭，在javascript中使用async.waterfall，该程序不会按预期结束。相反，它出现在“DB封闭的”线后，只是等待。

$ node test-async2.js 
hit connectMongo 
Connected correctly to server, DB: notes 
hit closeMongo 
DB closed 

[program just waits here, doesn't end] 

我期待的节目结束了。我在做什么错误？

const 
    async = require('async'), 
    MongoClient = require('mongodb').MongoClient, 
    url = 'mongodb://localhost:27017/notes';  

function connectMongo(next) { 
    console.log('hit connectMongo'); 
    MongoClient.connect(url, function(err, db) { 
    console.log("Connected to server, DB: " + db.databaseName); 
    next(null, db); 
    }); 
} 

function closeMongo(db, next) { 
    console.log('hit closeMongo'); 
    db.close; 
    next(null, "DB closed"); 
} 

// perform connect then close sequentially 
async.waterfall([ 
    connectMongo, 
    closeMongo, 
], function (err, result) { 
    if (err) throw err; 
    console.log(result); 
}); 

Answer 1

尝试db.close（）代替db.close

此外，添加一个回调db.close检查错误而关闭。