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revealjs-embed-code

This repository contains a small and simple js plugin for embedding code files into revealjs presentations, without the need to copy and paste their contents into the presentation file.

The idea and basic design is based off of a repository from dafrenchyman.

A somewhat similar, but still different approach, can be found in this repository.

Features

  • include code from files without copy-pasting it into your presentation
<code data-url="link-to-code-file"></code>
  • specify line numbers to limit the range of the file to be included
<code data-url="link-to-code-file" data-line-start="2" data-line-end="10"></code>
  • automatically remove a common indentation in every line (especially useful for highly indented lines in the middle of code files)
<!-- in your presentation in the browser -->
<div>
    <p>This is a test</p>
</div>

instead of

<!-- your code file -->
            <div>
                <p>This is a test</p>
            </div>
  • use delimiters instead of fix line numbers to allow for dynamic code listings, in case the code file changes
<!-- your presentation -->
<code data-url="test.html" data-line-start-delimiter="listing-1" data-line-end-delimiter="listing-1-end"></code>
<!-- your code file: test.html -->
<p>Here is some HTML</p>

<!-- listing-1 -->
<p>This HTML should be listed!</p>
<p>And this too!</p>
<!-- listing-1-end -->

<p>But this not anymore</p>
<!-- in your presentation in the browser -->
<code>
    <p>This HTML should be listed!</p>
    <p>And this too!</p>
</code>

Installation

Prerequisites

This plugin requires the presentation to be served via a webserver, for more information see Why is a web server required?.

In case you need a local webserver just for presenting or working on the presentation, I recommend steps at How to install a local web server?.

Copy plugin

To get started, first copy the embed-code.js file into the plugin folder of your revealjs presentation.

Link into presentation

Then, link the js file into your main html file before your script section that calls Reveal.initialize(), e.g. like this

<script src="plugin/embed-code.js"></script>

Now, tell revealjs to load the plugin

plugins: [
    RevealMarkdown,
    EmbedCode,
    RevealHighlight,
    ...
],

In case you also use e.g. RevealHighlight, make sure to load the EmbedCode plugin first, as the code content must be embedded first before it can be used by other plugins.
If you want to use the plugin with the markdown code syntax, you can do so by loading the RevealMarkdown plugin first.

That's it! Now you can use the plugin in your presentation.

Usage

To use this plugin, you just have to specify the data-url attribute with a url to the desired text file in a code tag in your presentation.

<code data-url="plugin/revealjs-external-code/external-code.js"></code>

This includes the whole file into the code tag.

There are more parameters to specify which range of the file should be included.

Attribute Value Description
data-url URL specifies that this code has dynamically loaded content and the URL at which it can be found
data-line-start number the number of the first line to be included
data-line-end number the number of the last line to be included
data-line-start-delimiter string a string that can be used to dynamically specify the first line to be included. The plugin searches each line for an occurrence of this string and uses the first one it finds
data-line-end-delimiter string a string that can be used to dynamically specify the last line to be included. The plugin searches each line for an occurrence of this string and uses the first one it finds
data-no-beautify none specifies whether the included code should be beautified, i.e. remove a common indentation in all lines
data-include-delimiters none specifies whether the lines where the delimiters were found should be included or not

Why is a web server required?

Unfortunately, a web server is required to load these external code files into your presentation.

This is due to the mitigation of several security vulnerabilities. Basically, each locally server file opened by your browser is its own 'domain' and therefore no other file can be loaded by js without triggering a CORS error. This cannot be circumvented, also not by using <iframe> or <object> tags.

More information can be found here.

How to install a local web server?

The easiest way to get a local webserver up and running is likely via the python module http.server (in python2 it's HttpServer). As it is bundled with python by default, it can simply be started with

python -m http.server

That's it! If you want to use the comfort of auto-reloading, I'd recommend the usage of the npm package live-server, which is explained in the following part.

Local Webserver with Live Reload

Install nodejs and then initialize a new package with

npm init -y

This creates a package.json file in your current directory, which you can basically ignore.

Now, install and start a local webserver

npm install live-server
node node_modules/live-server/live-server.js

Assuming that you presentation file lies in you current working directory and has the filename index.html, it should now being opened in your web browser at the address http://127.0.0.1:8080/.

After making changes and saving them into your presentation file, the website should reload automatically.

For more information take a look here.