用socket.io显示[ object ]的rethinkdb变更提要

Question

我正在使用express.js，rethinkdb，thinky，socket.io。尝试将数据库中发生的任何更改通知索引页。所以我使用rethinkdb changesfeed (我可以在console.log中看到更新)，但是游标/提要显示的是对象对象而不是数据。

当我将提要结果传递给socket.emit时，它会显示对象吗？我阅读并实现了来自rethinkdb博客(https://www.rethinkdb.com/blog/cats-of-instagram/)的代码，但它不起作用。

请用socket.io头向下滚动到底部

App.js

 var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var r = require('rethinkdb');

// ***********  Thinky code*********************//
var changeStream = require("rethinkdb-change-stream");
var thinky = require('thinky')()
var type = thinky.type;
var r = thinky.r;

//thinky model
var User = thinky.createModel('User', {
      author: type.string()
});

/*
User.changes().then(function (feed) {
    feed.each(function (error, doc) {
        if (error) {
            console.log(error);
            process.exit(1);
        }

        if (doc.isSaved() === false) {
            console.log("The following document was deleted:");
            console.log(JSON.stringify(doc));
        }
        else if (doc.getOldValue() == null) {
            console.log("A new document was inserted:");
            console.log(JSON.stringify(doc));
        }
        else {
            console.log("A document was updated.");
            console.log("Old value:");
            console.log(JSON.stringify(doc.getOldValue()));
            console.log("New value:");
            console.log(JSON.stringify(doc));
        }
    });
}).error(function (error) {
    console.log(error);
    process.exit(1);
});

*/
//*********End Thinky Code ******************//




// Mongodb Example http://www.guru99.com/node-js-mongodb.html
var MongoClient = require('mongodb').MongoClient
var url = 'mongodb://localhost/EmployeeDB';


var routes = require('./routes/index');
var users = require('./routes/users');

var app = express();
//attach socket server to express server so it interacts with clients requests and responses
app.io = require('socket.io')();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(require('stylus').middleware(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', routes);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function (req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function (err, req, res, next) {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: err
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function (err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
        message: err.message,
        error: {}
    });
});


/*    )))))))))))))))) socket.io Header (((((((((((((((((((    */

    app.io.on('connection', function (socket) {
        r.connect(host = 'localhost', port = 28015, db = 'test').then(function (conn) {
            this.conn = conn;
            return r.table("User").changes().run(this.conn).then(function (cursor) {
                cursor.each(function (err, item) {
                    console.log(item);
                    //if (item && item.new_val)
                       socket.emit("message-from-server", { greeting: item });
                });
            })
        });
        // socket.emit("message-from-server", { greeting: "Say whatever here- it will show on the index page"});
    });


  module.exports = app;

Answer 1

从你的代码：

console.log(item);
//if (item && item.new_val)
socket.emit("message-from-server", { greeting: item });

这告诉我，item可能是一个对象，所以当您将它传递给web以添加到DOM时，它会呈现对象引用[object Object]，因为它需要一个字符串(而不是一个对象)。因此，您可以使用对象的item语法或数组的[<index>]语法从item.toString()中提取您想要的信息，或者您可以做一些类似于item.toString()的操作，尝试将整个事件转换为字符串。它实际上取决于item的结构以及如何将它添加到DOM中。您可以在客户端完成，也可以在服务器发出之前执行。