Playground

In this guide you'll let readers run your examples without leaving the docs. With the playground feature on, a code block grows an "Open Code in" button in its header that opens the code — prefilled — in CodePen, JSFiddle, or CodeSandbox. It all happens in the reader's browser (a form POST for CodePen/JSFiddle, a parameterized link for CodeSandbox) — no backend, no API key.

The same @playground tag also gives you two presentation touches that work with or without providers: a filename header label and line highlighting.

1. Turn it on

The feature is off until you add playground to your jsdoc.json opts. The shorthand true turns it on with defaults (every provider, opt-in per example); the object form gives you control:

CODE

opts: {
  template: "./node_modules/clean-jsdoc-theme",
  playground: {
    // Turn every @example into a playground (default false → opt-in per tag).
    enableForAllExamples: false,
    // Which providers to offer, in this order (default: all three).
    providers: ["codepen", "jsfiddle", "codesandbox"],
    // Site-wide per-provider options (see "Set provider options" below).
    codepen: { js_pre_processor: "babel", css_external: "https://unpkg.com/some.css" },
    jsfiddle: { resources: "https://unpkg.com/some.js", wrap: "b" },
    codesandbox: { dependencies: { lodash: "latest" } }
  }
}

A few things to know:

playground: false (or omitting it) keeps output byte-identical — code blocks render exactly as before.
enableForAllExamples: true opts every @example in (an example can still opt out with @playground none).
providers sets the default set + order. Omit it for all three.

2. Tag an example

Add @playground to a doc comment, next to an @example. The grammar is a list of whitespace-separated tokens (the same parser as @iframe):

CODE

/**
 * Resize an image to a target width.
 *
 * @example
 * const out = resize(img, 200);
 * render(out);
 * @playground codepen jsfiddle filename=resize.js highlight=2
 */
export function resize(img, width) {}

Token	What it does
`codepen` / `jsfiddle` / `codesandbox`	Offer only these providers (your order is kept).
(bare `@playground`)	Use the default `providers` from `opts.playground`.
`none` / `off`	Opt this example out (handy with `enableForAllExamples`).
`filename=<name>`	Show `<name>` as the header label instead of `CODE`.
`highlight=1,4,8`	Highlight lines 1, 4 and 8 (1-based). `highlight=[1,4,8]` also works.

filename and highlight apply even with none/no providers — so you can label and highlight a snippet without offering a playground at all.

@playground is an unknown tag to base JSDoc, so set tags.allowUnknownTags: true in your jsdoc.json (the same flag @iframe needs) — otherwise JSDoc strips it before the theme runs. TypeDoc needs no such flag.

3. Use it in prose

Outside doc comments — in your docs folder, tutorials, or the README — there are two authoring forms, because of how prose is processed:

The ```js playground fence works in the docs directory and Markdown tutorials. Put playground (plus any tokens) after the language in the fence info string:

CODE

```js playground codepen filename=demo.js highlight=2
const out = resize(img, 200);
render(out);
```

The <playground> container works everywhere, including the README and HTML tutorials. Wrap a single fenced code block:

CODE

<playground codepen jsfiddle filename="demo.js" highlight="2">

```js
const out = resize(img, 200);
render(out);
```

</playground>

Why two forms? A fence's info string after the language (the "meta") is dropped when README/HTML prose is normalized, so the fence form only works for sources that arrive as raw Markdown (docs, Markdown tutorials). The <playground> container survives that normalization, so reach for it in the README. Leave a blank line around the inner fence (same rule as <steps>/<tabs>).

A bare prose playground (no provider tokens) offers all providers — prose has no access to the site-wide providers default.

4. Set provider options

The per-provider records in opts.playground are passed straight to each service's prefill API and apply to every playground on the site:

CodePen — the /pen/define prefill fields: js_pre_processor, js_external, css, css_external, html, editors, layout, title, … The example code becomes the pen's JS.
JSFiddle — the post API fields: resources (comma-separated external URLs), wrap, html, css, title, description.
CodeSandbox — the define API: dependencies seed package.json; the example becomes index.js.

To recolor the header strip or the highlighted-line tint, set the codeHeaderBg / codeHeaderFg / codeHighlightBg keys under colors / darkColors.

Playground

1. Turn it on

2. Tag an example

3. Use it in prose

4. Set provider options

See also