How to Customize Embedded Demos with Cody.js

Luis Manuel
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If you are a front-end developer, you often find yourself embedding demos in a website to showcase something. Maybe you are using any of the most popular embedded systems out there, like Codepen or JSFiddle. If that is the case, you must have noticed that available options for customization often are not enough.

These systems offers only a few options to customize the embedded demos (mostly colors). Codepen also offers an option to use your own stylesheet, but you need a PRO account (paid) for that.

Sometimes we need a little more freedom in the styles, in order to match more accurately the look and feel of the entire page we are building. So, I would like to introduce a little library to solve exactly this problem. Meet Cody:

Table of Contents

    Cody is a small library to embed demos for front-end developers. It has no dependencies and it's fully customizable.

    Along this tutorial we'll be exploring all the possible options that Cody offers. When we finish, you will be able to style your demos as much as you want :)

    If you are interested in how Cody works, I recommend you to start reading this article by Ben Frain. Of course, you can also check the full code on Github.

    When to use Cody

    Before seeing some code, let's first look at when and when not to use Cody.

    Some good reasons to USE Cody:

    • You need a fully customized embed. Something original, that does not look like all others.
    • You don't want to require external services, or host your code somewhere else.

    Some good reasons to NOT use Cody:

    • You don't need extra customization at all.
    • Your demo it's made up using not only plain HTML, CSS or JavaScript, and you want to show the source code as well (maybe SCSS or TypeScript).

    Now that it's clear when we can get the most out of this tool, let's see how to use it to get a working demo styled like this:

    Setting up the markup

    First step is to include the Cody scripts and styles in the head of the HTML document.

    <link rel="stylesheet" href="css/cody.css">
    <script src="js/cody.js"></script>

    Embedding a demo from Codepen

    You can embed a demo from Codepen easily using Cody. Just like:

    <!-- Attribute [data-pen]: The URL of the desired pen. -->
    <div class="cody" data-pen=""></div>

    Please note that in case the pen have external dependencies, you need to link them too as follows. That's because (for now) Codepen does not have an official API to get the pen settings, only the code in the editor.

    <!-- Attribute [data-css-assets]: External CSS dependencies. -->
    <!-- Attribute [data-js-assets]:  External JS dependencies. -->
    <div class="cody"

    Embedding a demo from anywhere

    To showcase local demos, or demos hosted elsewhere we can setup the HTML like the following:

    <div class="cody">
        <code class="html"></code>
        <code class="css" data-assets="css/normalize.css" data-code="css/demo.css"></code>
        <code class="js" data-assets="js/segment.min.js, js/d3-ease.v0.6.min.js" data-code="js/demo.js"></code>

    Let's explain what is happening here in detail for better understanding:

    • We have a wrapper (.cody), used later in JavaScript initialization.
    • We have an HTML element for each language (.html, .css and .js).
    • The attribute [data-code] link to the code that you want to show.
    • The attribute [data-assets] link to code that you don't want to show, but needed in execution. Useful for external libraries and dependencies.

    Here we have defined all the code using external files, but you can put the code directly inside each element as well. For example, the HTML code could have been defined as:

    <textarea class="html">
        <!-- HTML code of demo -->
        <button class="refresh-icon">
            <svg viewBox="0 0 90 90">
                <path class="circle-path" d="M 45 45 m 0 -30 a 30 30 0 1 1 0 60 a 30 30 0 1 1 0 -60"></path>
            <svg class="arrow-svg" viewBox="0 0 90 90">
                <path class="arrow-path" d="M 50 15 m -18 -18 l 18 18 l -18 18"></path>

    Initializing Cody in JavaScript

    With the HTML ready, we can initialize Cody as follows:

    // We need to set a base URL as we are using relative URLs
    var baseUrl = '';
    // The `init` function receive an object with options
        boxesHeight: 225,           // The boxes that will show the code and the result will have a `height = 225px`
        baseUrl: baseUrl,
        css: [
            'css/cody-basic.css',   // Basic styles
            'css/cody-classic.css', // Classic theme
            'css/prism-okaidia.css' // Highlight theme for Prism
        js: [
            'js/prism.js'           // Highlight library Prism

    You can see all available options documented in the Github repository.

    Overriding options

    Another way to define options is in the HTML (specifically in the wrapper). You can override any option you like setting it as data-*, and using "dash-case" format instead "camelCase". For example, if you want to override the resultTitle option, you need something like this:

    <div class="cody" data-result-title="The new result title">
        <!-- CODE HERE -->

    Customize as much as you like

    Now we know the basics about Cody, let's see how we can use it to achieve a little more tuned designs.

    Applying a different theme

    This time we are going to see how to achieve this style for our demo:

    As you can see, we are changing lots of things here. Let's see:

    • We are using a different highlight theme.
    • We set line numbers in the code.
    • We change the title for the tabs, to use SVG icons instead.
    • We are showing the demo (result) in a different box.

    Check the code that made it possible (only JavaScript was changed):

        target: '.cody-custom',     // Our wrapper this time
        selected: 'html',           // HTML will be the selected tab at the beginning
        tabsSpace: false,           // We don't want space for tabs (because we are positioning it as `absolute` in CSS)
        lineNumbers: true,          // We want line numbers for the code
        // The following are SVG icons to replace the tab titles
        htmlTitle: '<svg xmlns="" viewBox="0 0 128 128" class="devicon"><path d="M9.032 2l10.005 112.093 44.896 12.401 45.02-12.387 10.015-112.107h-109.936zm89.126 26.539l-.627 7.172-.276 3.289h-52.665000000000006l1.257 14h50.156000000000006l-.336 3.471-3.233 36.119-.238 2.27-28.196 7.749v.002l-.034.018-28.177-7.423-1.913-21.206h13.815000000000001l.979 10.919 15.287 4.081h.043v-.546l15.355-3.875 1.604-17.579h-47.698l-3.383-38.117-.329-3.883h68.939l-.33 3.539z"/></svg>',
        cssTitle: '<svg xmlns="" viewBox="0 0 128 128" class="devicon"><path d="M8.76 1l10.055 112.883 45.118 12.58 45.244-12.626 10.063-112.837h-110.48zm89.591 25.862l-3.347 37.605.01.203-.014.467v-.004l-2.378 26.294-.262 2.336-28.36 7.844v.001l-.022.019-28.311-7.888-1.917-21.739h13.883l.985 11.054 15.386 4.17-.004.008v-.002l15.443-4.229 1.632-18.001h-32.282999999999994l-.277-3.043-.631-7.129-.331-3.828h34.748999999999995l1.264-14h-52.926l-.277-3.041-.63-7.131-.332-3.828h69.281l-.331 3.862z"/></svg>',
        jsTitle: '<svg xmlns="" viewBox="0 0 128 128" class="devicon"><path d="M2 1v125h125v-125h-125zm66.119 106.513c-1.845 3.749-5.367 6.212-9.448 7.401-6.271 1.44-12.269.619-16.731-2.059-2.986-1.832-5.318-4.652-6.901-7.901l9.52-5.83c.083.035.333.487.667 1.071 1.214 2.034 2.261 3.474 4.319 4.485 2.022.69 6.461 1.131 8.175-2.427 1.047-1.81.714-7.628.714-14.065-.001-10.115.046-20.188.046-30.188h11.709c0 11 .06 21.418 0 32.152.025 6.58.596 12.446-2.07 17.361zm48.574-3.308c-4.07 13.922-26.762 14.374-35.83 5.176-1.916-2.165-3.117-3.296-4.26-5.795 4.819-2.772 4.819-2.772 9.508-5.485 2.547 3.915 4.902 6.068 9.139 6.949 5.748.702 11.531-1.273 10.234-7.378-1.333-4.986-11.77-6.199-18.873-11.531-7.211-4.843-8.901-16.611-2.975-23.335 1.975-2.487 5.343-4.343 8.877-5.235l3.688-.477c7.081-.143 11.507 1.727 14.756 5.355.904.916 1.642 1.904 3.022 4.045-3.772 2.404-3.76 2.381-9.163 5.879-1.154-2.486-3.069-4.046-5.093-4.724-3.142-.952-7.104.083-7.926 3.403-.285 1.023-.226 1.975.227 3.665 1.273 2.903 5.545 4.165 9.377 5.926 11.031 4.474 14.756 9.271 15.672 14.981.882 4.916-.213 8.105-.38 8.581z"/></svg>',
        boxesHeight: 225,           // The boxes for code will have `height = 225px`
        resultAlwaysVisible: 200,   // The result will be showed in a different box, always visible and will have `height = 200px`
        baseUrl: baseUrl,
        css: [
            'css/cody-basic.css',           // Basic styles
            'css/cody-modern.css',          // Modern theme (tabs with position `absolute`, etc.)
            'css/prism.css',                // Default highlight theme for Prism
            'css/prism-line-numbers.css',   // Prism styles for plugin line numbers
            // Some additional styles for the SVG icons. Yes, you can put code here, not only links!
            '.devicon{height:21px;margin-top:7px}.devicon path{fill:rgba(255,255,255,0.9)}'
        js: [
            'js/prism.js',                  // Highlight library Prism
            'js/prism-line-numbers.min.js'  // Prism plugin to get line numbers

    Showing only the result

    But, what if you want to show only the result (not the code) in a creative way like this?

    It's just a matter of removing everything we do not need in initialization, and adding some additional HTML and CSS for the background. The JavaScript part looks like this:

        target: '.cody-nexus',      // Our wrapper this time
        tabsVisible: false,         // We don't need tabs this time, we just want to show the selected one (HTML by default)
        boxesHeight: 400,           // The box will have `height = 400px`
        baseUrl: baseUrl,
        css: ['css/cody-basic.css'] // We just need the basic styles

    Using a different highlight library

    In all of our examples we are using Prism to highlight the code. That not mean you can't use any other you like. For example, let's see how to use highlight.js:

        css: [
            '/path/to/styles/default.css'     // highlight.js theme
        js: [
            '/path/to/highlight.pack.js',     // highlight.js library
            'hljs.initHighlightingOnLoad();'  // highlight.js initialization
        // Additional options...

    As you can see, inserting CSS and JavaScript as we need opens a lot of possibilities for customization.


    And that's all! You can see the demo showing all the examples we made along the tutorial. The code and full documentation can be found on the Github repo.

    Note that the development of this library is just starting out, and I'm sure there are lot of things to add and improve. Please do not hesitate to report any bug you find. And if you would like to contribute with the project you are more than welcome as well :)

    We really hope you have enjoyed the journey so far and found Cody useful!

    Luis Manuel

    12 posts

    Engineer in Computer Science and Freelance Front-End Developer. Available for Hire.