Typescript Playground Plugin Svelte

Easily create TypeScript Playground Plugins with Svelte.


Easily create TypeScript Playground Plugins with Svelte.

🚧 This project is experimental. If you have any ideas on how to improve this library, any contributions are welcomed. Also, TypeScript Playground plugins currently only work in Chromium based browsers.

Prefer React? Check out https://github.com/gojutin/typescript-playground-plugin-react.

Table Of Contents

  1. About
  2. Getting Started
  3. Props
  4. Styling Your Plugin
  5. More about TypeScript Playground Plugins


The TypeScript Playground V2 comes packed with lots of new features, including the ability to create plugins. Per the TypeScript docs:

The new TypeScript Playground allows people to hook into the Playground and extend it in ways in which the TypeScript team don't expect.

The sidebar of the Playground uses the same plugin infrastructure as external plugins, so you have the same level of access as the playground to build interesting projects.

Playground plugins have no fancy frameworks, you're free to inject them at runtime and use them if you need to - but the current plugins are built with the DOM APIs and TypeScript.

Since Svelte can be compiled down to dependency-free JavaScript classes, it offers a great, declarative alternative to writing imperative markup with the DOM APIs. This library allows you to use Svelte as a replacement or addition to the DOM APIs to create a rich, interactive UI for your plugin.

Getting Started

Step 1. Clone this repo and navigate to the directory

git clone git@github.com:gojutin/typescript-playground-plugin-svelte.git
cd typescript-playground-plugin-svelte

Step 2. Download dependencies

npm install

Step 3. Start the development server

npm start

This will start a development server in watch mode. As you edit any files in the src directory, the app will recompile and update dist/index.js, which is the file that is served to the TypeScript Playground.

Note: This does not reload the browser when your files change. In order to see your changes, the browser will need to be manually reloaded each time you make changes to the plugin.

Step 4. Configure and use your plugin

You can further customize your plugin by modifying the customPlugin object in src/index.ts. For instance, you can change the displayName property to change the label of the tab for your plugin. See the PlaygroundPlugin interface in vendor/playground.d.ts for all of the available options.

Visit https://www.typescriptlang.org/v2/en/play.

Select the Options tab and tick the box for Connect to localhost:5000/index.js.

Now, refresh the browser. When the playground reeoads, a new tab with your plugin should appear! 🎉


The TypeScript Playground Plugin API provides lifecycle methods that are used to interact with the playground. This library uses a combination of writable store objects and functions to provide the values and methods provided by these lifecycle methods to the Svelte app via props. The following props are provided to your Svelte app:


Writable store


Although this is writable store value, you don't want to write to it. See setCode and formatCode below.

The current code in the Monaco editor. This value updates on change to the Monaco editor with optional debouncing. Uses sandbox.getText().



(code: string, options: {format: boolean}) => void

Set the code in the Monaco editor with optional formatting. Uses sandbox.setText().



() => void

Format the code in the Monaco editor. Alias for sandbox.editor.getAction("editor.action.formatDocument").run().


Readable store


Alias for sandbox.monaco.editor.getModelMarkers({}). Kept in sync via sandbox.editor.onDidChangeModelDecorations.

Here is the type definition for IMarker:

interface IMarker {
  owner: string;
  resource: Uri;
  severity: MarkerSeverity;
    | string
    | {
        value: string;
        link: Uri;
  message: string;
  source?: string;
  startLineNumber: number;
  startColumn: number;
  endLineNumber: number;
  endColumn: number;
  relatedInformation?: IRelatedInformation[];
  tags?: MarkerTag[];



(debounce: boolean) => void

Optionally debounce the modelChange event from the Plugin API. Per the Plugin docs, this is run on a delay and may not fire on every keystroke. The code prop will be updated accordingly. Default is true.




A DOM library for interacting with TypeScript and JavaScript code, which powers the heart of the TypeScript playground. This object provides several properties and methods to interact with the playground. See all of the available types in src/plugin/vendor/sandbox.d.ts and read more about the sandbox at http://www.typescriptlang.org/v2/dev/sandbox/.


Writable store


The model is an object which Monaco uses to keep track of text in the editor. You can find the full type definition at node_modules/monaco-editor/esm/vs/editor/editor.api.d.ts. Although this is a writable store, you should not overwrite it.



The div element that wraps the entire sidebar. The Svelte app is mounted to this element. Any style changes to this element will affect the entire sidebar.



(code: string, subtitle?: string, links?: string[]) => void

From window.playground.ui - This function accepts three arguments (code, subtitle, and links) and opens a model with the values you provide.



(message: string) => void

From window.playground.ui - This function accepts one argument (message) and and flashes a quick message in the center of the screen.



  el: (str: string, el: string, container: Element) => void;, 
  requireURL: (path: string) => string;, 
  createASTTree: (node: Node) => HTMLDivElement;

An object that contains three additional config options and functionality. el, requireURL, and createASTTree. See src/plugin/vendor/pluginUtils.d.ts for more information.

You can access them in App.svelte like so:

  export let container;
  export let sandbox;
  export let model;
  export let useDebounce;
  export let code;
  export let setCode;
  export let formatCode;
  export let markers;
  export let showModal;
  export let flashInfo;
  export let utils;

Styling your plugin

Style you Svelte components as normal. All styles defined in your Svelte components are automatically injected into the page at render time. You can read more about styling Svelte components at https://svelte.dev/docs#style.

You can also apply styles to the container element. Be cautious as this will affect all tabs in the sidebar.

More about TypeScript Playground Plugins

Official Playground Plugin Documentation

You can create a plugin (without Svelte) from the official plugin template:

npm init typescript-playground-plugin playground-my-plugin

For convenience, this repo contains the CONTRIBUTING.md file included in the official plugin template. This document contains useful information about how to work with the plugins.

The src/vendor directory contains all of the TypeScript type definitions for the TypeScript Playground Plugin API. This is the best place to find the various config options, properties, and methods that are available.

Need inspiration?

Orta created a really cool plugin that lets you create presentations in the TypeScript playground using Reveal.js. You can check it out here:


He also offered these plugin ideas in this issue.

  • An LSP-ish Playground where you can make see the response to specific calls
  • An English explainer which explains a complex TS type
  • Convert TS dts -> Flow interfaces(flowgen)
  • Run tutorials in the playground against live code as a learning tool
  • AST Viewer
  • ts-query runner
  • codemod runner
  • Highlight TS vs JS (or type vs value) parts of some code code
  • Show all used types in a file
  • Show dts files in the current workspace
  • Edit an ambient dts file

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