db.collection不是函数（MongoDB 3+）

问题描述 投票：1回答：1

我正在使用MongoDB和Socket.io创建一个聊天应用程序;但是，我一直坚持这个问题很长一段时间。每次我运行我的服务器node server.js我都通过了console.log('MongoDB connected...);但是当它到达db.collection时会抛出一个错误，说它不是一个函数。

如果有人可以查看我的代码，看看我是否有任何错误。谢谢！

服务器端（server.js）

const mongo = require('mongodb').MongoClient;
const client = require('socket.io').listen(4000).sockets;

// connect to mongo

mongo.connect('mongodb://127.0.0.1/uchat', { useNewUrlParser: true }, function(err, db){
    if (err) {
        throw err;
    }

    console.log('MongoDB connected...');

    // connect to Socket.io
    client.on('connection', function(socket){
        let chat = db.collection('chats');

        // create function to send status
        sendStatus = function(s) {
            socket.emit('status', s);
        }

        // get chats from mongo collection
        chat.find().limit(100).sort({_id:1}).toArray(function(err, res) {
            if (err) {
                throw err;
            }

            // if no err emit the messages
            socket.emit('output', res);
        });

        // handle input events
        socket.on('input', function(data){
            let name = data.name;
            let message = data.message;

            // check for name and message
            if (name == '' || message == '') {
                // send error message
                sendStatus('Please enter a name and message.');
            } else {
                // insert message
                chat.insert({name: name, message: message}, function() {
                    client.emit('output', [data]);

                    // send status object
                    sendStatus({
                        message: 'Message sent',
                        clear: true
                    })
                });
            }
        });

        // handle clear messages
        socket.on('clear', function(data){
            // remove all chats from the collection
            chat.remove({}, function(){
                // let user know
                socket.emit('cleared');
            });
        });
    });
});

客户端（index.html）

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
    <style>
        #messages{height:300px;}
    </style>
    <title>uChat</title>
  </head>
  <body>
    <div class="container">
        <div class="row">
            <div class="col-md-6 offset-md-3 col-sm-12">
                <h1 class="text-center">
                    uChat
                    <button id="clear" class="btn btn-danger">Clear</button>
                </h1>
                <div id="status"></div>
                <div id="chat">
                    <input type="text" id="username" class="form-control" placeholder="Enter name...">
                    <br>
                    <div class="card">
                        <div id="messages" class="card-block">

                        </div>
                    </div>
                    <br>
                    <textarea id="textarea" class="form-control" placeholder="Enter message..."></textarea>
                </div>
            </div>
        </div>
    </div>

    <script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.2.0/socket.io.dev.js"></script>

    <script>
        (function(){
            var element = function(id) {
                return document.getElementById(id);
            }

            // get elements
            var status = element('status');
            var messages = element('messages');
            var textarea = element('textarea');
            var username = element('username');
            var clear = element('clear');

            // set default status
            var statusDefault = status.textContent;

            var setStatus = function(s) {
                // set status
                status.textContent = s;
                // if status doesn't equal default clear after 4s
                if (s !== statusDefault) {
                    var delay = setTimeout(function(){
                        setStatus(statusDefault);
                    }, 4000);
                }
            }

            // connect to Socket.io server
            var socket = io.connect('http://127.0.0.1:4000');

            // check for connection

            if (socket !== undefined) {
                console.log('Connected to Socket.io...');
            }
        })();
    </script>
  </body>
</html>

package.json文件

{
  "name": "uchat",
  "version": "1.0.0",
  "description": "Simple Chat App",
  "main": "server.js",
  "scripts": {
    "start": "node server.js"
  },
  "author": "Hunter Shaw",
  "license": "ISC",
  "dependencies": {
    "mongodb": "*",
    "socket.io": "*"
  }
}

我打算远程连接到我的服务器，因为我计划稍后使用我在PhoneGap上学到的东西。

谢谢您的帮助！

终端错误

$ node server.js
MongoDB connected...
C:\Users\hunte\Desktop\uChat\server.js:15
        let chat = db.collection('chats');
                      ^

TypeError: db.collection is not a function
    at Namespace.<anonymous> (C:\Users\hunte\Desktop\uChat\server.js:15:23)
    at Namespace.emit (events.js:182:13)
    at Namespace.emit (C:\Users\hunte\Desktop\uChat\node_modules\socket.io\lib\namespace.js:213:10)
    at C:\Users\hunte\Desktop\uChat\node_modules\socket.io\lib\namespace.js:181:14
    at process._tickCallback (internal/process/next_tick.js:61:11)
javascript node.js mongodb socket.io
1个回答
1
投票

它是，因为当你连接时，你没有得到err和db对象，你得到err和client对象。

基本上你要做的是：

let db = client.db("YOUR_DB_NAME")
let chat = db.collection("chat")

然后它应该工作。

您应该查看mongodb文档，尤其是连接示例here。

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