Launch – Make an Extension on a Mac

Today we are “extending” the “Launch – Make an Extension” mini series. This article arose out of a lab I ran at the Adobe Summit in London. There is a lot of overlap, but two major differences, too:

1. This article walks you through building an Extension on a Mac and using Visual Studio Code
2. The Extension contains an Action

I feel that the first difference in itself justifies a second article. Visual Studio Code is a pretty cool editor (I’m almost tempted to use it for coding and downgrade Sublime to be my text editor at this point), too.

The Extension is very simple, again. In this case, it contains just one single Action, a simple one at that.

Start by installing Visual Studio Code and npm, both straight-forward installers on Macs.


Extensions are little packages. They follow a format, based on CommonJS modules, which means there are a couple of configuration files we need to provide.

Thankfully, this is in large part automated.

Create a project folder first

1. Open a Terminal window
2. Type the following commands:

mkdir dev
mkdir dev/sampleextension
cd dev/sampleextension

If there are no errors, you should have created two folders, as follows:

Create a Project Folder
You can close the Terminal now, if you want. We’ll handle any other command line work within our editor.

3. Start Visual Studio Code
4. Click “Open Folder…” on the left, choose the folder you made, click “Open”

Visual Studio Code – just after launch
Open our Folder in Visual Studio Code
We are now ready to make our Extension.

5. From the “View” menu, select “Integrated Terminal”

Integrated Terminal Menu in Visual Studio Code
As a result, you will have a command line on the bottom right of Visual Studio Code

Visual Studio Code with Integrated Terminal
The next step is the semi-automatic creation of the extension project structure.

6. Type npm init into the terminal
7. Provide reasonable answers for the prompts (feel free to follow the screenshot below)

npm init command
8. At the final prompt, press `Enter`

We now have a basic structure, note that there is now a file in your folder called “package.json”.

package.json file

9. Type npm install @adobe/reactor-scaffold --save-dev into the command line
10. Type node_modules/.bin/reactor-scaffold into the command line
11. Provide reasonable answer at the prompts (feel free to follow the screenshot below)

Scaffolding – halfway through
The scaffolding tool now presents you with a sort of menu. You can navigate the menu with the up and down arrow keys, and select an option using `enter`

12. Move down to “Add an action type” and press `enter`
13. Provide reasonable answers at the prompts. “Alert” is a good display name and make sure you say “y” to the second question!

Scaffolding – with Action
14. Move down to the “I’m done” line and press enter

The scaffolding tool will create a couple of files and folders. Most notably, it will create two files named after your Action’s name. In my case, those are “alert.html” and “alert.js”

Scaffolding – finished


For context, this is how Launch, by Adobe uses Extensions.

Extensions Flow
The “alert.html” file is used by Launch to enable users to provide configuration. The “alert.js” file is what will be delivered into the web site that uses Launch.


We will provide code for both, the HTML and Javascript, files.


When we open the “alert.html” file, it looks pretty empty. We will provide some HTML to create a form. Users of our plugin should be able to input the text for our alert, plus a delay in seconds.

15. Click onto the “alert.html” file to open it in an editor
16. Copy the code below into the file, replacing the “Action Template” line

<h1>Jan's Alert Action</h1>

        <label for="message">What message shall we pop up?</label>
        <input type="text" name="message">
        <label for="delay">How long before we pop up?</label>
        <input type="number" name="delay">

This is the result

alert.html file
Underneath, you can see three Javascript functions. Each Extension has to provide those functions, they are how Launch interacts with your configuration page.

17. Copy the code below, replacing the whole <script> block

    init: function(info) { 
        if (info.settings) { 
            document.getElementsByName("message")[0].value = info.settings.message; 
            document.getElementsByName("delay")[0].value = info.settings.delay; 
    getSettings: function()
        return { 
            message: document.getElementsByName("message")[0].value, 
            delay: parseInt( document.getElementsByName("delay")[0].value + "", 10) 
    validate: function() { 
        var message = document.getElementsByName("message")[0].value; 
        var delay = document.getElementsByName("delay")[0];
        var tmp = delay.value + ""; 
        var numericalDelay = tmp - 0; 
        var valid = false; 
        if ('undefined' !== typeof message && message && message.length > 0 
          && 'undefined' !== typeof numericalDelay && 0 < numericalDelay) { 
        return valid; 

This is the result

Script in the HTML File

Debugging – the Sandbox

We have to test our code, and there is a tool for that, the “Reactor Sandbox”.

18. Type npm install @adobe/reactor-turbine @adobe/reactor-sandbox --save-dev into your command line
19. Open the “package.json” file by clicking it.
20. Find the “scripts” block in the file, note it contains one line
21. At the end of the line, type `,`, followed by `enter`
22. paste this into the new line: "sandbox": "reactor-sandbox"
23. Type node_modules/.bin/reactor-sandbox init into the command line

npm will install some packages, and your “package.json” file should look like this:

package.json with sandbox
24. Type npm run sandbox into the command line.

npm run sandbox
We just launched a Launch-specific test environment on our machines, which we can see using a browser.

25. Open a new tab in your browser
26. Type `localhost:3000` into the URL

Sandbox View
Moving on to the other file.

Coding, part 2


The “alert.js” file contains the code that Launch will deliver into the site. This code has to actually make our Action happen.

1. Copy the following code into the “alert.js” file

'use strict'; 
var extensionSettings = turbine.getExtensionSettings(); 
module.exports = function (settings) { 
    if (settings.message) { 
        setTimeout(function() { 
        }, settings.delay); 

The file should look like this

The Javascript can be debugged using the Sandbox, too. There is some setup to do, though.

1. Open the “container.js” file in the “.sandbox” folder
2. Replace the content with the code below

'use strict'; 
module.exports = { 
    rules: [ 
        name: 'Example Rule', 
        events: [ 
            // This is a simple event type provided by the sandbox which triggers the rule 
            // as soon as the DTM library is loaded. This event type is provided as a 
            // convenience in case your extension does not have event types of its own. 
            modulePath: 'sandbox/pageTop.js', 
            settings: {} 
        } ], 
        actions: [ 
            modulePath: 'jans-alert-action/src/lib/actions/alert.js', 
            settings: { 
                delay: 10000, 
                message: "Hi there!" 
        } ] 
    } ], 
    extensions: { 
        // Set up an extension configuration you would like to test. The top-level object key is the 
        // name of your extension (as defined in your extension.json). 
        'jans-alert-action': { 
            displayName: "Jan's Alert Action" 
    property: { 
        name: 'Sandbox property', 
        settings: { 
            domains: [ '', '' ], 
            linkDelay: 100, 
            euCookieName: 'sat_track', 
            undefinedVarsReturnEmpty: false 
    buildInfo: { 
        turbineVersion: "25.1.0", 
        turbineBuildDate: "2018-04-12T18:10:34Z", 
        buildDate: "2018-03-30T16:27:10Z",
        environment: "development" 

This “container.js” file simulates a Launch Property. It contains one Rule, triggered at Page Top (or Library Load), and one Action (our Action). You can now in the Sandbox click over to the Library Sandbox, and you should see an alert after 10 seconds.

Library Sandbox View

Further Reading

If you want to know more, here are a couple of resources

Launch Extension Guides
Launch-by-Adobe blog (technical)
Miniseries on Launch Extensions on

When you are done with your Extension, and you are considering making it public, speak to Jeff Chasin.

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