javascript - 使用 Node.js 驱动程序打印和更新 MongoDB 中的所有文档

Question

我正在编写一个脚本，该脚本应该获取集合中文档的数量，然后将它们全部打印出来，然后更新它们中的每一个，问题是我在运行它时遇到错误:MongoError:连接按申请关闭。这是我的代码，我尝试将 db.close() 放在几个没有帮助的地方。

var request = require('request');
var cheerio = require ('cheerio');
var fs = require('fs');
var MongoClient = require('mongodb').MongoClient;

var dbName = "yahooStocks";
var port = "27017";
var requiredCollection = "stocks"
var host = "localhost";


MongoClient.connect("mongodb://" + host + ":" + port + "/" + dbName, function (error, db){

        if(error) throw error;
        console.log ("Connected to: " + "mongodb://" + host + ":" + port + "/" + dbName);
    function update () {

        db.collection(requiredCollection).count({}, function (error, numOfDocs) {
            if(error) throw error;
            console.log("the number of docs is : " , numOfDocs);

            for (i=1; i<10; i++) {
                var findOneQuery = {'_id' : i};
                db.collection(requiredCollection).findOne(findOneQuery, function (error, doc) {
                    if(error) throw error;

                    console.log(doc._id + ". Doc - > " , doc);

                }); // end of findOne

                //db.close();
            }

             db.close();
        }); // end of count




    }
update();
// db.close();
 }); // end of connection to MongoClien

Answer 1

您需要确保以异步方式运行这些查询。最好的方法是使用异步库。 (本例使用 Mongoose )

使用异步库:https://github.com/caolan/async

var queries = [];

for (i=1; i<10; i++) {
    queries.push(db.collection(requiredCollection).findOne({'_id' : i}));
}

async.each(queries, function(query, callback) {
    query.exec(function(err, doc) {
      if (err) callback(err);

      console.log(doc._id + ". Doc - > " , doc);

      // do things here

      callback();
    });
}, function(err) {
    // when everything is complete.
});