javascript - TypeError : dbObject.集合不是函数

Question

我正在尝试从数据库中获取数据，但卡在某个点上。我收到此错误，但我不知道出了什么问题。我试图找到解决方案但仍然没有得到适当的答案。我正在尝试从本教程中实现它。

https://www.fusioncharts.com/dev/using-with-server-side-languages/tutorials/creating-interactive-charts-using-node-express-and-mongodb

这是我的代码:

//import express package
var express = require("express");

//import mongodb package
var mongodb = require("mongodb");

//MongoDB connection URL - mongodb://host:port/dbName
var dbHost = "mongodb://localhost:27017/fusion_demo";

//DB Object
var dbObject;

//get instance of MongoClient to establish connection
var MongoClient = mongodb.MongoClient;

//Connecting to the Mongodb instance.
//Make sure your mongodb daemon mongod is running on port 27017 on localhost
MongoClient.connect(dbHost, function(err, db){
  if ( err ) throw err;
  dbObject = db;
  console.log('connect to server');
 // console.log(db);
});

function getData(responseObj){
  //use the find() API and pass an empty query object to retrieve all records
  dbObject.collection("fuel_price").find({}).toArray(function(err, docs){
    if ( err ) throw err;
    var monthArray = [];
    var petrolPrices = [];
    var dieselPrices = [];

    for ( index in docs){
      var doc = docs[index];
      //category array
      var month = doc['month'];
      //series 1 values array
      var petrol = doc['petrol'];
      //series 2 values array
      var diesel = doc['diesel'];
      monthArray.push({"label": month});
      petrolPrices.push({"value" : petrol});
      dieselPrices.push({"value" : diesel});
    }

    var dataset = [
      {
        "seriesname" : "Petrol Price",
        "data" : petrolPrices
      },
      {
        "seriesname" : "Diesel Price",
        "data": dieselPrices
      }
    ];

    var response = {
      "dataset" : dataset,
      "categories" : monthArray
    };
    responseObj.json(response);
  });
}

//create express app
var app = express();

//NPM Module to integrate Handlerbars UI template engine with Express
var exphbs  = require('express-handlebars');

//Declaring Express to use Handlerbars template engine with main.handlebars as
//the default layout
app.engine('handlebars', exphbs({defaultLayout: 'main'}));
app.set('view engine', 'handlebars');

//Defining middleware to serve static files
app.use('/public', express.static('public'));
app.get("/fuelPrices", function(req, res){
  getData(res);
});
app.get("/", function(req, res){
  res.render("chart");
});

app.listen("3300", function(){
  console.log('Server up: http://localhost:3300');
});

Answer 1

dbObject 为 null，因此没有收集方法。可能 Mongo DB 未运行或正在不同的端口中运行。检查 MongoDB 是否正确启动并运行，并且您可以连接到它。