Embeddable Javascript widgets

Github gists example

Github gists are great and easy to share. Simply paste their embed code onto any page.

<!-- Embed code -->
<script src="https://gist.github.com/BrianSigafoos/f0fe5e6417b0acf70ffe1bc6b6498796.js"></script>

The response from that script simply does 2 things using document.write():

1. Add a stylesheet
2. Add the HTML tags to render the gist content.

// Endpoint Response to .js code above
document.write(
  '<link rel="stylesheet" href="https://github.githubassets.com/assets/gist-embed-5687a589e344.css" />'
)
document.write(
  '<div id="gist74791356" class="gist">\n <div class="gist-file" translate="no">...</div></div></ div>\n'
)

Recreating it in Rails

The code to embed the widget is simple:

<div class="demoapp demoapp-widget">
  <script src="http://lvh.me:3000/widgets/mKVEFN.js"></script>
  <p>Widget created with <a href="https://github.com/BrianSigafoos/docker-rails-webpacker-app">Docker Rails Demo App</a> by Brian</p>
</div>

And here is a widget rendered below. Note: this only works locally for now via this repo.

How it works

• Add a new route resources :widgets, only: :show
• Add the new WidgetsController with skip_before_action :verify_authenticity_token and layout false with a show.js.erb like this
• Add the rack-cors gem to allow CORS with a config/initializers/cors.rb like this
• Add the widget CSS via a new widget.scss like this
  • You’ll want to scope the CSS to only your app :where(.demoapp) { ... }, for example
• Add code to generate the copyable widget snippet
• Add code to preview the widget snippet in your app, without any CSS on that page
• Use something like Hugo (that powers this blog) to locally create a page and then embed the snippet. This will confirm CORS is set up correctly as the widget is called from the local Hugo-served page and to the local Rails endpoint.