.. _extension_tutorial: Let's Make an Astronomy Picture of the Day JupyterLab Extension ---------------------------------------------------------------- JupyterLab extensions add features to the user experience. This page describes how to create one type of extension, an *application plugin*, that: - Adds a "Random `Astronomy Picture `__" command to the *command palette* sidebar - Fetches the image and metadata when activated - Shows the image and metadata in a tab panel By working through this tutorial, you'll learn: - How to set up an extension development environment from scratch on a Linux or OSX machine. (You'll need to modify the commands slightly if you are on Windows.) - How to start an extension project from `jupyterlab/extension-cookiecutter-ts `__ - How to iteratively code, build, and load your extension in JupyterLab - How to version control your work with git - How to release your extension for others to enjoy .. figure:: extension_tutorial_complete.png :align: center :class: jp-screenshot :alt: The completed extension, showing the Astronomy Picture of the Day for 24 Jul 2015. The completed extension, showing the `Astronomy Picture of the Day for 24 Jul 2015 `__. Sound like fun? Excellent. Here we go! Set up a development environment ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Install conda using miniconda ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Start by installing miniconda, following `Conda's installation documentation `__. .. _install-nodejs-jupyterlab-etc-in-a-conda-environment: Install NodeJS, JupyterLab, etc. in a conda environment ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Next create a conda environment that includes: 1. the latest release of JupyterLab 2. `cookiecutter `__, the tool you'll use to bootstrap your extension project structure (this is a Python tool which we'll install using conda below). 3. `NodeJS `__, the JavaScript runtime you'll use to compile the web assets (e.g., TypeScript, CSS) for your extension 4. `git `__, a version control system you'll use to take snapshots of your work as you progress through this tutorial It's best practice to leave the root conda environment (i.e., the environment created by the miniconda installer) untouched and install your project-specific dependencies in a named conda environment. Run this command to create a new environment named ``jupyterlab-ext``. .. code:: bash conda create -n jupyterlab-ext -c conda-forge --override-channels jupyterlab cookiecutter nodejs git Now activate the new environment so that all further commands you run work out of that environment. .. code:: bash conda activate jupyterlab-ext Note: You'll need to run the command above in each new terminal you open before you can work with the tools you installed in the ``jupyterlab-ext`` environment. Create a repository ~~~~~~~~~~~~~~~~~~~ Create a new repository for your extension (see, for example, the `GitHub instructions `__. This is an optional step, but highly recommended if you want to share your extension. Create an extension project ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Initialize the project from a cookiecutter ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Next use cookiecutter to create a new project for your extension. This will create a new folder for your extension in your current directory. .. code:: bash cookiecutter https://github.com/jupyterlab/extension-cookiecutter-ts --checkout v1.0 When prompted, enter values like the following for all of the cookiecutter prompts (``apod`` stands for Astronomy Picture of the Day, the NASA service we are using to fetch pictures). :: author_name []: Your Name extension_name [myextension]: jupyterlab_apod project_short_description [A JupyterLab extension.]: Show a random NASA Astronomy Picture of the Day in a JupyterLab panel repository [https://github.com/my_name/jupyterlab_myextension]: https://github.com/my_name/jupyterlab_apod Note: if not using a repository, leave the repository field blank. You can come back and edit the repository field in the ``package.json`` file later. Change to the directory the cookiecutter created and list the files. .. code:: bash cd jupyterlab_apod ls You should see a list like the following. :: README.md package.json src style tsconfig.json Build and install the extension for development ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Your new extension project has enough code in it to see it working in your JupyterLab. Run the following commands to install the initial project dependencies and install it in the JupyterLab environment. We defer building since it will be built in the next step. .. note:: This tutorial uses ``jlpm`` to install Javascript packages and run build commands, which is JupyterLab's bundled version of ``yarn``. If you prefer, you can use another Javascript package manager like ``npm`` or ``yarn`` itself. .. code:: bash jlpm install jupyter labextension install . --no-build After the install completes, open a second terminal. Run these commands to activate the ``jupyterlab-ext`` environment and to start a JupyterLab instance in watch mode so that it will keep up with our changes as we make them. .. code:: bash conda activate jupyterlab-ext jupyter lab --watch See the initial extension in action ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ After building with your extension, JupyterLab should open in your default web browser. In that browser window, open the JavaScript console by following the instructions for your browser: - `Accessing the DevTools in Google Chrome `__ - `Opening the Web Console in Firefox `__ After you reload the page with the console open, you should see a message that says ``JupyterLab extension jupyterlab_apod is activated!`` in the console. If you do, congratulations, you're ready to start modifying the extension! If not, go back make sure you didn't miss a step, and `reach out `__ if you're stuck. Note: Leave the terminal running the ``jupyter lab --watch`` command open. Commit what you have to git ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Run the following commands in your ``jupyterlab_apod`` folder to initialize it as a git repository and commit the current code. .. code:: bash git init git add . git commit -m 'Seed apod project from cookiecutter' Note: This step is not technically necessary, but it is good practice to track changes in version control system in case you need to rollback to an earlier version or want to collaborate with others. For example, you can compare your work throughout this tutorial with the commits in a reference version of ``jupyterlab_apod`` on GitHub at https://github.com/jupyterlab/jupyterlab_apod. Add an Astronomy Picture of the Day widget ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Show an empty panel ^^^^^^^^^^^^^^^^^^^ The *command palette* is the primary view of all commands available to you in JupyterLab. For your first addition, you're going to add a *Random Astronomy Picture* command to the palette and get it to show an *Astronomy Picture* tab panel when invoked. Fire up your favorite text editor and open the ``src/index.ts`` file in your extension project. Change the import at the top of the file to get a reference to the command palette interface and the Jupyter front end. .. code:: typescript import { JupyterFrontEnd, JupyterFrontEndPlugin } from '@jupyterlab/application'; import { ICommandPalette } from '@jupyterlab/apputils'; You will also need to install these dependencies. Run the following commands in the repository root folder install the dependency and save it to your `package.json`: .. code:: bash jlpm add @jupyterlab/apputils jlpm add @jupyterlab/application Locate the ``extension`` object of type ``JupyterFrontEndPlugin``. Change the definition so that it reads like so: .. code:: typescript /** * Initialization data for the jupyterlab_apod extension. */ const extension: JupyterFrontEndPlugin = { id: 'jupyterlab_apod', autoStart: true, requires: [ICommandPalette], activate: (app: JupyterFrontEnd, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_apod is activated!'); console.log('ICommandPalette:', palette); } }; The ``requires`` attribute states that your plugin needs an object that implements the ``ICommandPalette`` interface when it starts. JupyterLab will pass an instance of ``ICommandPalette`` as the second parameter of ``activate`` in order to satisfy this requirement. Defining ``palette: ICommandPalette`` makes this instance available to your code in that function. The second ``console.log`` line exists only so that you can immediately check that your changes work. Run the following to rebuild your extension. .. code:: bash jlpm run build JupyterLab will rebuild after the extension does. You can see it's progress in the ``jupyter lab --watch`` window. After that finishes, return to the browser tab that opened when you started JupyterLab. Refresh it and look in the console. You should see the same activation message as before, plus the new message about the ICommandPalette instance you just added. If you don't, check the output of the build command for errors and correct your code. :: JupyterLab extension jupyterlab_apod is activated! ICommandPalette: Palette {_palette: CommandPalette} Note that we had to run ``jlpm run build`` in order for the bundle to update, because it is using the compiled JavaScript files in ``/lib``. If you wish to avoid running ``jlpm run build`` after each change, you can open a third terminal, and run the ``jlpm run watch`` command from your extension directory, which will automatically compile the TypeScript files as they change. Now return to your editor. Modify the imports at the top of the file to add a few more imports: .. code:: typescript import { ICommandPalette, MainAreaWidget } from '@jupyterlab/apputils'; import { Widget } from '@phosphor/widgets'; Install this new dependency as well: .. code:: bash jlpm add @phosphor/widgets Then modify the ``activate`` function again so that it has the following code: .. code-block:: typescript activate: (app: JupyterFrontEnd, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_apod is activated!'); // Create a blank content widget inside of a MainAreaWidget const content = new Widget(); const widget = new MainAreaWidget({content}); widget.id = 'apod-jupyterlab'; widget.title.label = 'Astronomy Picture'; widget.title.closable = true; // Add an application command const command: string = 'apod:open'; app.commands.addCommand(command, { label: 'Random Astronomy Picture', execute: () => { if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.add(widget, 'main'); } // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({command, category: 'Tutorial'}); } The first new block of code creates a ``MainAreaWidget`` instance with an empty content ``Widget`` as its child. It also assigns the main area widget a unique ID, gives it a label that will appear as its tab title, and makes the tab closable by the user. The second block of code adds a new command with id ``apod:open`` and label *Random Astronomy Picture* to JupyterLab. When the command executes, it attaches the widget to the main display area if it is not already present and then makes it the active tab. The last new line of code uses the command id to add the command to the command palette in a section called *Tutorial*. Build your extension again using ``jlpm run build`` (unless you are using ``jlpm run watch`` already) and refresh the browser tab. Open the command palette on the left side by clicking on *Commands* and type *Astronomy* in the search box. Your *Random Astronomy Picture* command should appear. Click it or select it with the keyboard and press *Enter*. You should see a new, blank panel appear with the tab title *Astronomy Picture*. Click the *x* on the tab to close it and activate the command again. The tab should reappear. Finally, click one of the launcher tabs so that the *Astronomy Picture* panel is still open but no longer active. Now run the *Random Astronomy Picture* command one more time. The single *Astronomy Picture* tab should come to the foreground. .. figure:: extension_tutorial_empty.png :align: center :class: jp-screenshot :alt: The in-progress extension, showing a blank panel. The in-progress extension, showing a blank panel. If your widget is not behaving, compare your code with the reference project state at the `01-show-a-panel tag `__. Once you've got everything working properly, git commit your changes and carry on. .. code-block:: bash git add . git commit -m 'Show Astronomy Picture command in palette' Show a picture in the panel ^^^^^^^^^^^^^^^^^^^^^^^^^^^ You now have an empty panel. It's time to add a picture to it. Go back to your code editor. Add the following code below the lines that create a ``MainAreaWidget`` instance and above the lines that define the command. .. code-block:: typescript // Add an image element to the content let img = document.createElement('img'); content.node.appendChild(img); // Get a random date string in YYYY-MM-DD format function randomDate() { const start = new Date(2010, 1, 1); const end = new Date(); const randomDate = new Date(start.getTime() + Math.random()*(end.getTime() - start.getTime())); return randomDate.toISOString().slice(0, 10); } // Fetch info about a random picture const response = await fetch(`https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&date=${randomDate()}`); const data = await response.json() as APODResponse; if (data.media_type === 'image') { // Populate the image img.src = data.url; img.title = data.title; } else { console.log('Random APOD was not a picture.'); } The first two lines create a new HTML ```` element and add it to the widget DOM node. The next lines define a function get a random date in the form ``YYYY-MM-DD`` format, and then the function is used to make a request using the HTML `fetch `__ API that returns information about the Astronomy Picture of the Day for that date. Finally, we set the image source and title attributes based on the response. Now define the ``APODResponse`` type that was introduced in the code above. Put this definition just under the imports at the top of the file. .. code-block:: typescript interface APODResponse { copyright: string; date: string; explanation: string; media_type: 'video' | 'image'; title: string; url: string; }; And update the ``activate`` method to be ``async`` since we are now using ``await`` in the method body. .. code-block:: typescript activate: async (app: JupyterFrontEnd, palette: ICommandPalette) => Rebuild your extension if necessary (``jlpm run build``), refresh your browser tab, and run the *Random Astronomy Picture* command again. You should now see a picture in the panel when it opens (if that random date had a picture and not a video). .. figure:: extension_tutorial_single.png :align: center :class: jp-screenshot The in-progress extension, showing the `Astronomy Picture of the Day for 19 Jan 2014 `__. Note that the image is not centered in the panel nor does the panel scroll if the image is larger than the panel area. Also note that the image does not update no matter how many times you close and reopen the panel. You'll address both of these problems in the upcoming sections. If you don't see a image at all, compare your code with the `02-show-an-image tag `__ in the reference project. When it's working, make another git commit. .. code:: bash git add . git commit -m 'Show a picture in the panel' Improve the widget behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Center the image, add attribution, and error messaging ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Open ``style/index.css`` in our extension project directory for editing. Add the following lines to it. .. code-block:: css .my-apodWidget { display: flex; flex-direction: column; align-items: center; overflow: auto; } This CSS stacks content vertically within the widget panel and lets the panel scroll when the content overflows. This CSS file is included on the page automatically by JupyterLab because the ``package.json`` file has a ``style`` field pointing to it. In general, you should import all of your styles into a single CSS file, such as this ``index.css`` file, and put the path to that CSS file in the ``package.json`` file ``style`` field. Return to the ``index.ts`` file. Modify the ``activate`` function to apply the CSS classes, the copyright information, and error handling for the API response. The beginning of the function should read like the following: .. code-block:: typescript :emphasize-lines: 6,16-17,28-50 activate: async (app: JupyterFrontEnd, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_apod is activated!'); // Create a blank content widget inside of a MainAreaWidget const content = new Widget(); content.addClass('my-apodWidget'); // new line const widget = new MainAreaWidget({content}); widget.id = 'apod-jupyterlab'; widget.title.label = 'Astronomy Picture'; widget.title.closable = true; // Add an image element to the content let img = document.createElement('img'); content.node.appendChild(img); let summary = document.createElement('p'); content.node.appendChild(summary); // Get a random date string in YYYY-MM-DD format function randomDate() { const start = new Date(2010, 1, 1); const end = new Date(); const randomDate = new Date(start.getTime() + Math.random()*(end.getTime() - start.getTime())); return randomDate.toISOString().slice(0, 10); } // Fetch info about a random picture const response = await fetch(`https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&date=${randomDate()}`); if (!response.ok) { const data = await response.json(); if (data.error) { summary.innerText = data.error.message; } else { summary.innerText = response.statusText; } } else { const data = await response.json() as APODResponse; if (data.media_type === 'image') { // Populate the image img.src = data.url; img.title = data.title; summary.innerText = data.title; if (data.copyright) { summary.innerText += ` (Copyright ${data.copyright})`; } } else { summary.innerText = 'Random APOD fetched was not an image.'; } } // Keep all the remaining fetch and command lines the same // as before from here down ... Build your extension if necessary (``jlpm run build``) and refresh your JupyterLab browser tab. Invoke the *Random Astronomy Picture* command and confirm the image is centered with the copyright information below it. Resize the browser window or the panel so that the image is larger than the available area. Make sure you can scroll the panel over the entire area of the image. If anything is not working correctly, compare your code with the reference project `03-style-and-attribute tag `__. When everything is working as expected, make another commit. .. code:: bash git add . git commit -m 'Add styling, attribution, error handling' Show a new image on demand ^^^^^^^^^^^^^^^^^^^^^^^^^^ The ``activate`` function has grown quite long, and there's still more functionality to add. Let's refactor the code into two separate parts: 1. An ``APODWidget`` that encapsulates the Astronomy Picture panel elements, configuration, and soon-to-be-added update behavior 2. An ``activate`` function that adds the widget instance to the UI and decide when the picture should refresh Start by refactoring the widget code into the new ``APODWidget`` class. Add the following additional import to the top of the file. .. code-block:: typescript import { Message } from '@phosphor/messaging'; Install this dependency: .. code:: bash jlpm add @phosphor/messaging Then add the class just below the import statements in the ``index.ts`` file. .. code-block:: typescript class APODWidget extends Widget { /** * Construct a new APOD widget. */ constructor() { super(); this.addClass('my-apodWidget'); // new line // Add an image element to the panel this.img = document.createElement('img'); this.node.appendChild(this.img); // Add a summary element to the panel this.summary = document.createElement('p'); this.node.appendChild(this.summary); } /** * The image element associated with the widget. */ readonly img: HTMLImageElement; /** * The summary text element associated with the widget. */ readonly summary: HTMLParagraphElement; /** * Handle update requests for the widget. */ async onUpdateRequest(msg: Message): Promise { const response = await fetch(`https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&date=${this.randomDate()}`); if (!response.ok) { const data = await response.json(); if (data.error) { this.summary.innerText = data.error.message; } else { this.summary.innerText = response.statusText; } return; } const data = await response.json() as APODResponse; if (data.media_type === 'image') { // Populate the image this.img.src = data.url; this.img.title = data.title; this.summary.innerText = data.title; if (data.copyright) { this.summary.innerText += ` (Copyright ${data.copyright})`; } } else { this.summary.innerText = 'Random APOD fetched was not an image.'; } } You've written all of the code before. All you've done is restructure it to use instance variables and move the image request to its own function. Next move the remaining logic in ``activate`` to a new, top-level function just below the ``APODWidget`` class definition. Modify the code to create a widget when one does not exist in the main JupyterLab area or to refresh the image in the exist widget when the command runs again. The code for the ``activate`` function should read as follows after these changes: .. code-block:: typescript /** * Activate the APOD widget extension. */ function activate(app: JupyterFrontEnd, palette: ICommandPalette) { console.log('JupyterLab extension jupyterlab_apod is activated!'); // Create a single widget const content = new APODWidget(); const widget = new MainAreaWidget({content}); widget.id = 'apod-jupyterlab'; widget.title.label = 'Astronomy Picture'; widget.title.closable = true; // Add an application command const command: string = 'apod:open'; app.commands.addCommand(command, { label: 'Random Astronomy Picture', execute: () => { if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.add(widget, 'main'); } // Refresh the picture in the widget content.update(); // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({ command, category: 'Tutorial' }); } Remove the ``activate`` function definition from the ``JupyterFrontEndPlugin`` object and refer instead to the top-level function like this: .. code-block:: typescript const extension: JupyterFrontEndPlugin = { id: 'jupyterlab_apod', autoStart: true, requires: [ICommandPalette], activate: activate }; Make sure you retain the ``export default extension;`` line in the file. Now build the extension again and refresh the JupyterLab browser tab. Run the *Random Astronomy Picture* command more than once without closing the panel. The picture should update each time you execute the command. Close the panel, run the command, and it should both reappear and show a new image. If anything is not working correctly, compare your code with the `04-refactor-and-refresh tag `__ to debug. Once it is working properly, commit it. .. code:: bash git add . git commit -m 'Refactor, refresh image' Restore panel state when the browser refreshes ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ You may notice that every time you refresh your browser tab, the Astronomy Picture panel disappears, even if it was open before you refreshed. Other open panels, like notebooks, terminals, and text editors, all reappear and return to where you left them in the panel layout. You can make your extension behave this way too. Update the imports at the top of your ``index.ts`` file so that the entire list of import statements looks like the following: .. code-block:: typescript :emphasize-lines: 2,6 import { ILayoutRestorer, JupyterFrontEnd, JupyterFrontEndPlugin } from '@jupyterlab/application'; import { ICommandPalette, MainAreaWidget, WidgetTracker } from '@jupyterlab/apputils'; import { Message } from '@phosphor/messaging'; import { Widget } from '@phosphor/widgets'; Install this dependency: .. code:: bash jlpm add @phosphor/coreutils Then add the ``ILayoutRestorer`` interface to the ``JupyterFrontEndPlugin`` definition. This addition passes the global ``LayoutRestorer`` as the third parameter of the ``activate`` function. .. code-block:: typescript :emphasize-lines: 4 const extension: JupyterFrontEndPlugin = { id: 'jupyterlab_apod', autoStart: true, requires: [ICommandPalette, ILayoutRestorer], activate: activate }; Finally, rewrite the ``activate`` function so that it: 1. Declares a widget variable, but does not create an instance immediately. 2. Constructs a ``WidgetTracker`` and tells the ``ILayoutRestorer`` to use it to save/restore panel state. 3. Creates, tracks, shows, and refreshes the widget panel appropriately. .. code-block:: typescript function activate(app: JupyterFrontEnd, palette: ICommandPalette, restorer: ILayoutRestorer) { console.log('JupyterLab extension jupyterlab_apod is activated!'); // Declare a widget variable let widget: MainAreaWidget; // Add an application command const command: string = 'apod:open'; app.commands.addCommand(command, { label: 'Random Astronomy Picture', execute: () => { if (!widget) { // Create a new widget if one does not exist const content = new APODWidget(); widget = new MainAreaWidget({content}); widget.id = 'apod-jupyterlab'; widget.title.label = 'Astronomy Picture'; widget.title.closable = true; } if (!tracker.has(widget)) { // Track the state of the widget for later restoration tracker.add(widget); } if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.add(widget, 'main'); } widget.content.update(); // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({ command, category: 'Tutorial' }); // Track and restore the widget state let tracker = new WidgetTracker>({ namespace: 'apod' }); restorer.restore(tracker, { command, name: () => 'apod' }); } Rebuild your extension one last time and refresh your browser tab. Execute the *Random Astronomy Picture* command and validate that the panel appears with an image in it. Refresh the browser tab again. You should see an Astronomy Picture panel reappear immediately without running the command. Close the panel and refresh the browser tab. You should then not see an Astronomy Picture tab after the refresh. .. figure:: extension_tutorial_complete.png :align: center :class: jp-screenshot :alt: The completed extension, showing the Astronomy Picture of the Day for 24 Jul 2015. The completed extension, showing the `Astronomy Picture of the Day for 24 Jul 2015 `__. Refer to the `05-restore-panel-state tag `__ if your extension is not working correctly. Make a commit when the state of your extension persists properly. .. code:: bash git add . git commit -m 'Restore panel state' Congratulations! You've implemented all of the behaviors laid out at the start of this tutorial. Now how about sharing it with the world? .. _publish-your-extension-to-npmjsorg: Publish your extension to npmjs.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ npm is both a JavaScript package manager and the de facto registry for JavaScript software. You can `sign up for an account on the npmjs.com site `__ or create an account from the command line by running ``npm adduser`` and entering values when prompted. Create an account now if you do not already have one. If you already have an account, login by running ``npm login`` and answering the prompts. Next, open the project ``package.json`` file in your text editor. Prefix the ``name`` field value with ``@your-npm-username>/`` so that the entire field reads ``"name": "@your-npm-username/jupyterlab_apod"`` where you've replaced the string ``your-npm-username`` with your real username. Review the homepage, repository, license, and `other supported package.json `__ fields while you have the file open. Then open the ``README.md`` file and adjust the command in the *Installation* section so that it includes the full, username-prefixed package name you just included in the ``package.json`` file. For example: .. code:: bash jupyter labextension install @your-npm-username/jupyterlab_apod Return to your terminal window and make one more git commit: .. code:: bash git add . git commit -m 'Prepare to publish package' Now run the following command to publish your package: .. code:: bash npm publish --access=public Check that your package appears on the npm website. You can either search for it from the homepage or visit ``https://www.npmjs.com/package/@your-username/jupyterlab_apod`` directly. If it doesn't appear, make sure you've updated the package name properly in the ``package.json`` and run the npm command correctly. Compare your work with the state of the reference project at the `06-prepare-to-publish tag `__ for further debugging. You can now try installing your extension as a user would. Open a new terminal and run the following commands, again substituting your npm username where appropriate (make sure to stop the existing ``jupyter lab --watch`` command first): .. code:: bash conda create -n jupyterlab-apod jupyterlab nodejs conda activate jupyterlab-apod jupyter labextension install @your-npm-username/jupyterlab_apod jupyter lab You should see a fresh JupyterLab browser tab appear. When it does, execute the *Random Astronomy Picture* command to prove that your extension works when installed from npm. Learn more ~~~~~~~~~~ You've completed the tutorial. Nicely done! If you want to keep learning, here are some suggestions about what to try next: - Add the image description that comes in the API response to the panel. - Assign a default hotkey to the *Random Astronomy Picture* command. - Make the image a link to the picture on the NASA website (URLs are of the form ``https://apod.nasa.gov/apod/apYYMMDD.html``). - Make the image title and description update after the image loads so that the picture and description are always synced. - Give users the ability to pin pictures in separate, permanent panels. - Add a setting for the user to put in their `API key `__ so they can make many more requests per hour than the demo key allows. - Push your extension git repository to GitHub. - Learn how to write :ref:`other kinds of extensions `.