Using Node.js to retrieve data from Redis through an AJAX request

Question

I'm going through a Node, Express, & Socket.io chat tutorial. I decided to use Redis to store the chat history and have successfully set it up so that my information is correctly posting to the database. I am now trying to access that information to use on the client-side (in this case I'm trying to access the list of users currently in the chat so I can show them to the side of the chat). I am using $.getJSON to make a GET request. Right now I have it setup so that the file it tries to access only has this JSON object : {"dog" : "2","cat":"3"} just to test it, and that is working, but I'm not sure where to go from there because anytime I try adding a function into that file, even if I specify to return a JSON object and call that function, the request stops returning the correct information.

For example I tried :

var data = function(){
    return {"dog" : "2","cat":"3"}
}
data();

and that doesn't return anything ( I understand that when I make a GET request the function isn't run, but it doesn't even return that text, and if it doesn't run a function than I'm not sure how I can access redis from this file)

Here's what I'm thinking:

var redis = require('redis')

//figure out how to access the redis client that I have at localhost:6379, something like var db = redis.X

//and then call (for example) db.smembers('onlineUsers') and be returned the object which I can iterate through

Here's my relevant code:

server.js:

var jade = require('jade');
var PORT = 8080;

var redis = require('redis');
var db = redis.createClient();
var pub = redis.createClient();
var sub = redis.createClient();

var http = require('http');
var express = require('express');
var app = express();
var server = http.createServer(app);
var io = require('socket.io').listen(server);
server.listen(PORT, function(){
  console.log("Now connected on localhost:" + PORT)
});

app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.set("view options", {layout: false});
app.use(express.static(__dirname + '/public'));
app.get('/', function(req, res){
 res.render('home');
});

io.sockets.on('connection', function(client){

  sub.subscribe("chatting");
  sub.on("message", function (channel, message) {
        console.log("message received on server from publish");
        client.send(message);
    });

  client.on("sendMessage", function(msg) {
            pub.publish("chatting",msg);
        });

  client.on("setUsername", function(user){
            pub.publish("chatting","A new user in connected:" + user);
            db.sadd("onlineUsers",user);
        }
    );

  client.on('disconnect', function () {
        sub.quit();
        pub.publish("chatting","User is disconnected :" + client.id);
    });
});

script.js:

$(document).ready( function(){
    $client = io.connect();
    initialize();
});


var setUsername = function(){
    var username = $("#usernameInput").val();
    if (username)
    {
        var user = username;
        $client.emit('setUsername', username);
        $('#chatControls').show();
        $('#usernameInput').hide();
        $('#usernameSet').hide();
        showCurrentUsers();
    }
}

var showCurrentUsers = function(){
    $('#list_of_users').empty();

    $.getJSON('getusers.js', function(data){
        for (var i = 0; i < data.length; i++){
            $('list_of_users').append("<li>"+data[i]+"</li>")
        }
    })

}

var sendMessage = function(){
    var msg = $('#messageInput').val();
    var username = $("#usernameInput").val();
    if (msg)
    {
        var data = {msg: msg, user: username}
        $client.emit('message', data);
        addMessage(data);
        $('#messageInput').val('');
        // populate(username,msg);
    }
}


var addMessage = function(data) {
    $("#chatEntries").append('<div class="message"><p>' + data.user + ' : ' + data.msg + '</p></div>');
}


// var populate = function(username,msg) {
//     var data ;
// }

var initialize = function(){
    $("#chatControls").hide();
    $("#usernameSet").on('click', setUsername);
    $("#submit").on('click',sendMessage);
    showCurrentUsers();
}

and right now all that the getusers.js file has in it is:

{"dog" : "2","cat":"3"}

I updated my answer below with some different JQuery to try. I hope it helps! — ctlacko
– ctlacko, Commented Jun 27, 2014 at 17:03

quoo · Accepted Answer · 2014-06-27 17:28:58Z

3

It looks like you're expecting your call to $.getJSON to load and execute the javascript it loads. It doesn't work this way. You need to make a node endpoint (via a route) which renders the JSON. The node endpoint would then do the data manipulation / querying redis:

Node:

In routes.js:

app.get('/chatdata', ChatController.getChatData);

In ChatController.js (manipulate, create the data as you like here)

exports.getChatData = function (req, res) {
   var data = function(){
      return {"dog" : "2","cat":"3"}
   };
   res.JSON(data);
};

Front-end

$.getJSON('getChatData', function(data){
    //...
})

edited Jun 27, 2014 at 17:28

answered Jun 27, 2014 at 17:08

quoo

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Comments

ctlacko · Accepted Answer · 2014-06-27 14:52:28Z

0

I think you need to setup a route to handle the GET request that $.getJSON makes, or if getusers.js is in the /public directory, then you need to modify your $.getJSON call as follows:

$.getJSON('http://localhost:8080/public/getusers.js', function(data){

answered Jun 27, 2014 at 14:52

ctlacko

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3 Comments

a_stout_man Over a year ago

I changed it to that, it still isn't returning the JSON from the page, I'm not sure if I'm requesting it incorrectly?

ctlacko Over a year ago

Where is getusers.js located in the directory structure?

a_stout_man Over a year ago

In the public folder, I'm referencing the file correctly because when I reference it incorrectly it tells me that it can't find the page I specified, but it isn't actually returning the data.

ctlacko · Accepted Answer · 2014-06-27 17:02:55Z

0

Ok, it looks like it is a problem with your getusers.js file. $.getJSON seems to prefer double quotes. Try formatting it like this:

{ "dog" : "2", "cat" : "3" }

Also, try using this to display the data:

    $.getJSON('getusers.js', function(data){
        var items = [];
        $.each( data, function( key, val ) {
            items.push("<li id='" + key + "'>" + val +"</li>");
        });
        $('#list_of_users').append(items.join(""));
    });

edited Jun 27, 2014 at 17:02

answered Jun 27, 2014 at 15:41

ctlacko

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