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How to Build a Public Anonymous Chat App in JavaScript

Curious how to build an app which allows you to send messages anonymously to friends or strangers nearby? Using Javascript and Pusher you can! Learn how with this tutorial from Peter Mbanugo.

Jan 10, 2019 • 12 Minute Read


We're all familiar with instant messaging and using it to chat with people in real-time. Sometimes, though, we might want an app which allows us to send messages anonymously to friends or to chat anonymously with strangers nearby. An example of such an app is Truth, which lets you talk with people on your contact list without disclosing your identity.

In this tutorial, I'll be showing you how to build a public anonymous chat app in JavaScript (using NodeJS and Express on the server, and VanillaJS on the client) and Pusher. Pusher allows us to build scalable and reliable real-time applications, and since we need real-time delivery of chat messages, this is a key component of the chat app. The image below depicts what we will be building:

Getting Started

Let's kick off by signing up for a free Pusher account (or logging in if you already have one). Once you're logged in, create a new Pusher app from the dashboard and make a note of your App ID, Key and Secret, which are unique to an app.

To create a new Pusher app, click the Your apps side menu, then click the Create a new app button below the drawer. This brings up the setup wizard.

  1. Enter a name for the application. In this case, I’ll call it “chat”.
  2. Select a cluster.
  3. Select the option “Create app for multiple environments” if you want to have different instances for development, staging and production.
  4. Select Vanilla JS as the frontend and NodeJS as the backend.
  5. Complete the process by clicking Create App button to set up your app instance.

Code-up the server

We need a back-end which will serve our static files, accept messages from a client, and broadcast to other connected clients through Pusher. Our back-end will be written in NodeJS, so we need to set it up.

We need a package.json file and I'll add it by running the command below. I will use the defaults provided by hitting enter for every prompt.

      $ npm init

With the package.json file added, I'll install Express, body-parser, and Pusher npm packages. Run the following command

      $ npm install --save pusher express body-parser

With these packages installed, let's add a new file called server.js with the following content

      var express = require('express');
var bodyParser = require('body-parser');
var Pusher = require('pusher');

var app = express();
app.use(bodyParser.urlencoded({ extended: false }));

var pusher = new Pusher({ appId: "APP_ID", key: "APP_KEY", secret:  "APP_SECRET", cluster: "APP_CLUSTER" });'/message', function(req, res) {
  var message = req.body.message;
  pusher.trigger( 'public-chat', 'message-added', { message });

     res.sendFile('/public/index.html', {root: __dirname });

app.use(express.static(__dirname + '/public'));

var port = process.env.PORT || 5000;
app.listen(port, function () {
  console.log(`app listening on port ${port}!`)

With the code above, we have defined an endpoint, /message, which will be used by the client to send the message that it wants to another client using Pusher. The other routes are used to serve static files to be added later.

Replace the placeholder strings App ID, Secret and Key with the values from your Pusher dashboard.

Add this statement "start": "node server.js" in the script property of our package.json file. This will allow us start the server when we run npm start

Building the frontend

Moving on to the frontend, let's add a new folder called public. This folder will contain our page and JavaScript files. Add a new file called style.css with the content below, which will hold our style definition for the page.

      @import url("");
    list-style: none;
    margin: 0;
    padding: 0;

.chat li
    margin-bottom: 10px;
    padding-bottom: 5px;
    border-bottom: 1px dotted #B3A9A9;

.chat li.left .chat-body
    margin-left: 60px;

.chat li.right .chat-body
    margin-right: 60px;

.chat li .chat-body p
    margin: 0;
    color: #777777;

.panel .slidedown .glyphicon, .chat .glyphicon
    margin-right: 5px;

    overflow-y: scroll;
    height: 250px;

    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3);
    background-color: #F5F5F5;

    width: 12px;
    background-color: #F5F5F5;

    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,.3);
    background-color: #555;

Add another file called index.html with the markup below.

      <!DOCTYPE html>
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

    <!-- Optional theme -->
    <link rel="stylesheet" href="" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">


    <!-- Latest compiled and minified JavaScript -->
    <script src="" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>

    <link rel="stylesheet" href="style.css">
    <script src=""></script>
    <script src="index.js"></script>
    <div class="container">
    <div class="row form-group">
        <div class="col-xs-12 col-md-offset-2 col-md-8 col-lg-8 col-lg-offset-2">
            <div class="panel panel-primary">
                <div class="panel-heading">
                    <span class="glyphicon glyphicon-comment"></span> Anonymous Chat
                    <div class="btn-group pull-right">
                        <button type="button" class="btn btn-default btn-xs dropdown-toggle" data-toggle="dropdown">
                            <span class="glyphicon glyphicon-chevron-down"></span>
                        <ul class="dropdown-menu slidedown">
                            <li><a href=""><span class="glyphicon glyphicon-refresh">
                            <li><a href=""><span class="glyphicon glyphicon-ok-sign">
                            <li><a href=""><span class="glyphicon glyphicon-remove">
                            <li><a href=""><span class="glyphicon glyphicon-time"></span>
                            <li class="divider"></li>
                            <li><a href=""><span class="glyphicon glyphicon-off"></span>
                                Sign Out</a></li>
                <div class="panel-body body-panel">
                    <ul class="chat">

                <div class="panel-footer clearfix">
                    <textarea id="message" class="form-control" rows="3"></textarea>
                    <span class="col-lg-6 col-lg-offset-3 col-md-6 col-md-offset-3 col-xs-12" style="margin-top: 10px">
                        <button class="btn btn-warning btn-lg btn-block" id="btn-chat">Send</button>

<script id="new-message-other" type="text/template">
    <li class="left clearfix">
        <span class="chat-img pull-left">
            <img src="" alt="User Avatar" class="img-circle" />
        <div class="chat-body clearfix">

<script id="new-message" type="text/template">
    <li id="{{id}}" class="right clearfix">
        <div class="chat-body clearfix">


I'm using a template from bootsnipp which has been slightly modified to display just the name and message.

Add a new file called index.js with the content below. Remember to add the Pusher app details:

    var pusher = new Pusher('APP_SECRET', {
        cluster: 'APP_CLUSTER',
        encrypted: false

    let channel = pusher.subscribe('public-chat');
    channel.bind('message-added', onMessageAdded);

        const message = $("#message").val();


        //send message
        $.post( "http://localhost:5000/message", { message } );

    function onMessageAdded(data) {
        let template = $("#new-message").html();
        template = template.replace("{{body}}", data.message);


With the code in this file, we get the message to send from the page, and then call the server with the message. After that, we connect to Pusher by creating a new Pusher object with the App Secret and the Cluster that you set earlier.

We subscribe to a channel and an event named message-added. The channel is a public channel so it can be named any way you like. I've chosen to prefix mine with public- but that's just my own convention as there are no rules for a public channel. However, private channels are prefixed with private- and presence channels are prefixed with presence-. Read more about channels and channel types here.

We bind to the click event of the chat button on the page, then we retrieve the message from the textbox on the page, and then send it to the server with the username. With all we have setup, we can run start the app by running npm start. Here's a glimpse of how it works on my computer.

Wrapping Up

This guide demonstrated how you can use Pusher to allow website visitors send messages anonymously in real-time. You can find the code used in this GitHub repository. Hopefully, this demo sparked some other application ideas that could be implemented using Pusher's real-time services.

I hope you found this guide informative and engaging. Thank you for reading!

This was originally published on Pusher