Pen Settings

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

⚠️ This feature can only be used by logged in users.

Code Indentation


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              // --------------------------------
// Note: to make the DevToolAddon work, please make sure you access this codepen page through 'http' instead of 'https':
// https://codepen.io/bhou/pen/JbgprG

// ---------
// Please follow the steps to debug this app with collar dev tool
// 1. install collar-dev-server
// sudo npm install collar-dev-server
// 2. run collar-dev-server, type following command line:
// collar-dev-server
// 3. open http://localhost:7500
// 4. run this app
// 5. right click "delegate to double module" node, and select "show delegation"

collar.use(new DevToolAddon()) // comment this in production

// First, let's build a pipeline to double the input value
// and use "to" method to connect nodes as a pipeline
const ns1 = collar.ns('namespace1', {module: 'double'});
const filter = ns1.when('test "to" connection', s => {
  return s.get('value') % 2 === 0
const double = ns1.map('double the input value', s => {
  return s.new({    // use signal.new to create a new signal
    value: s.get('value') * 2
const log = ns1.do('log the signal', s => {


// Now create a host module to use the double module
// and use "through" method to delegate the processing
const ns2 = collar.ns('namespace2', {module: 'host'});
const filter2 = ns2.when('test "through" connection', s => {
  return s.get('value') % 2 === 0
const log2 = ns2.do('log the signal', s => {

  .through('delegate to double module', filter, log)

// You should see two pipelines on collar dev tool (http://localhost:7500),
// right click the "delegate to double module" node, and select "show delegation"

🕑 One or more of the npm packages you are using needs to be built. You're the first person to ever need it! We're building it right now and your preview will start updating again when it's ready.