Key Points

• Reveal.js is a popular HTML5 and CSS3 library for creating impressive web-based presentations that can be controlled in real time by multiple users.
• To create a multi-user presentation using Reveal.js, you need to set up an express.js server with Node.js, Yeoman, Grunt, and Bower and use Socket.IO to send and receive slide change events.
• Adding basic authentication in server-side code helps prevent unauthorized users from controlling presentations and provides alternative routes for unauthorized users.
• Reveal.js presentations can be further customized and enhanced with features such as WebRTC and can be made more interactive by embedding multimedia content, quizzes, votes and forms.

Say goodbye to the PowerPoint era and embrace modern web demonstrations! With the development of web technology and the improvement of browser performance, a demonstration library based on HTML5 and CSS3 has emerged. Reveal.js is one of the most popular libraries that create stunning presentations. The WebSocket standard defined in the HTML5 specification implements bidirectional full-duplex communication in the browser. Many JavaScript libraries simplify the use of WebSocket, and Socket.IO is one of the outstanding representatives. This article will explore how to create a Reveal.js presentation that can be controlled by multiple users and use Socket.IO to send and receive slide change events in real time (ignoring the slightly more complex multiplexer plugin that comes with Reveal.js).

Precautions

This article assumes that you have installed and can use the following libraries:

• Node.js
• Yeoman
• Grunt
• Bower

Initial Steps

First, we will set up an express.js server. Yeoman simplifies the installation and operation of express.js servers with the help of generators. So we first install yeoman express-generator using npm.

$ npm install –g generator-express

This will install express-generator globally. Now let's set up the server.

$ yo express

This will ask you which type of expression you should install. You can choose Basic or MVC; in our case we only need the basic settings. It will then install a bunch of npm modules along with bower.json and Gruntfile.js files.

Next, use grunt to start the express server.

$ grunt

Yeoman created a default app.js file for us with the settings needed to run the server. Also, note that it comes with a "watch" library that will track changes in the code and reload the server automatically, so we don't need to do this manually.

Before we proceed, we will use bower to install and set up the reveal.js library. Installing reveal.js is very simple and direct. Just issue the following command in the terminal.

$ bower install reveal.js --save

This will get the latest stable version of the reveal.js library from Github and install it in the public/components directory. The --save option will automatically update the dependency part of the bower.json file using reveal.js.

Now we have everything we need to create a presentation server. We will start with the first slide of creating the presentation. To do this, create an HTML file in the views folder. (The HTML code is omitted here, which is consistent with the original text)

This HTML contains the CSS and JavaScript files for Reveal.js. Reveal.initialize() converts the above HTML into a beautiful presentation. Any part of the div element with the slides class will act as a slide.

Before we start the demo, we need to set up the server to serve this file according to the request. Therefore, we will update app.js with the following code. (The app.js code is omitted here, which is consistent with the original text)

The first line of code requires necessary dependencies from the server, and then creates an express object. The next line configures the public folder as a static directory where the server will look for requests for the static file. Then we add a route to provide the index.html file and start the server. Now we can view the presentation in the browser using the http://localhost:3000/ URL. But that's not what we really need. We need this presentation to be multiplexed so that when one user changes the slide, it should be reflected on another user's browser. Next, we will install and set up the Socket.io module to enable two-way communication using Websockets. (The Socket.IO related code is omitted here, which is consistent with the original text, including the security part)

You can find the full source code from Github.

Summary

In this article, we have seen how to build a simple Reveal.js presentation that can be controlled by multiple users. Here we use the Socket.IO library to update all connected clients in real time. We also added basic security to prevent unauthorized users from controlling the presentation. You can add more features and use technologies like WebRTC to make it more popular, so I hope you can see that this article is just the beginning.

(The FAQ part is omitted here, which is consistent with the original text)

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