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# State

> **Studio writes this format for you.** Every entry you create in the [Data panel](/docs/studio/logic/data), whether a value, a computed entry, a data source or a function, is saved as one of the shapes on this page.

`state` is the root-level object holding everything a document knows at runtime: mutable values, derived values, functions, and data sources. Every entry is reactive by default: change a value and everything bound to it updates. The **shape** of each entry determines what it is; no extra flags are needed in the common case.

```json shiki
```

![Jx Studio Data panel listing a component's state and functions](/content/docs/images/state-panel.png)

## Shape 1: naked values

A JSON scalar, array, or plain object with no reserved keys is a mutable reactive value, initialized to exactly what you wrote:

```json shiki
```

A plain string counts as a naked value only when it contains no ${}; otherwise it is Shape 3.

## Shape 2: typed values

An object with a `default` property (and no `$prototype`) is a typed value. `default` supplies the initial value; `type` references a JSON Schema, either inline or via `$ref` to `$defs`:

```json shiki
```

Schema keywords are tooling-only. They drive validation, autocomplete, and which Studio control edits the entry, then are stripped before runtime. The `format` keyword picks a specialized Studio input without changing the runtime value:

```json shiki
```

Use the typed form when the value needs constraints, documentation, or a shared type; use naked values when none apply.

## Shape 3: computed templates

A string containing ${} is a **computed** value, recalculated automatically whenever the state it reads changes:

```json shiki
```

The text inside ${} is a pure expression over `state`: no statements, no assignments, no `return`. For computed values built without expression syntax at all, see [Expressions](/docs/framework/concepts/expressions).

When the whole string is one ${}, the entry holds the expression's own value: `isEmpty` above is a real boolean, so ${state.isEmpty ? 'Nothing yet' : ''} works as written, and "${state.count \* 2}" is a number. Put any text around it, or use two ${}, and the entry is a string, the way `scoreLabel` is `"90%"`. The editor, the built page and a component that comes alive in the browser all read an entry the same way.

## Shape 4: prototypes

An object with `$prototype` declares a function or a data source. Functions use `$prototype: "Function"` with an inline `body` or an external `$src` (see [Functions](/docs/framework/concepts/functions)); any other constructor name declares a data source (see [Data prototypes](/docs/framework/concepts/data-prototypes)):

```json shiki
```

Data-source entries always resolve reactively. An object with `$expression` is the fifth, fully declarative shape: a computed value or handler built from structure instead of a code string ([Expressions](/docs/framework/concepts/expressions)).

## Private entries

A `#` prefix marks an entry as private, meaning internal workings that are never exposed to the Studio property panel, never included in tooling exports, and never settable via `$props`:

```json shiki
```

Private is enforced, not just conventional. A parent that names one in `$props`, or passes it as a `props.#cache` attribute or a JS property, has the write **ignored**, with a console warning naming the entry. The instance still renders: a private key in `$props` is a mistake worth pointing at, not a reason to blank the component. The custom element also gets no `#cache` property, so there is no back door around the check.

Rename the entry without the `#` if you meant it to be part of the component's interface.

## How it works

At load time the runtime walks `state` once, classifying each entry by inspection in a fixed order: a string containing ${ is computed; any other scalar or array is a naked value; an object is checked for `$expression`, then `$prototype`, then `default`; a plain object with no reserved keys is a naked object value. The whole scope is initialized inside a reactive proxy, computed templates become tracked computed values, and inside function bodies state is read and written directly (`state.count`, `state.items.push(...)`), with no getter or setter calls.

## Rules

- Every entry is reactive by default; there is no opt-in flag.
- Shape follows from inspection alone: a string with ${} is *always* computed, an object with `default` and no `$prototype` is *always* a typed value.
- Computed templates must be pure expressions: no statements, no assignments, no semicolons, no `return`.
- `state` inside a template refers only to the current document's scope, never a parent's.
- Entry names are `camelCase` (`count`, `firstName`, `handleInput`); types in `$defs` are `PascalCase` (`TodoItem`).
- `#`-prefixed entries are private: hidden from props and tooling exports.
- On a Function entry, `body` and `$src` are mutually exclusive.

## Related

- [Reactivity](/docs/framework/concepts/reactivity): how ${} bindings track dependencies
- [Expressions](/docs/framework/concepts/expressions): the declarative Shape 5
- [Functions](/docs/framework/concepts/functions): Function entries, sidecars, and statements
- [Data prototypes](/docs/framework/concepts/data-prototypes): Request, LocalStorage, collections
- [Data panel](/docs/studio/logic/data): the Studio surface that writes these entries

✕

Start here[Overview](/docs/start/)Get started[Install Jx Studio](/docs/start/install/)[Your first project](/docs/start/first-project/)[A tour of Jx Studio](/docs/start/studio-tour/)Tutorials[Tutorial: interactive component](/docs/start/first-component/)[Tutorial: blog with collections](/docs/start/first-collection/)[Video tutorials](/docs/start/videos/)Coming from another tool[Coming from WordPress](/docs/start/coming-from-wordpress/)[Coming from Webflow or Framer](/docs/start/coming-from-webflow/)[Coming from Wix or Squarespace](/docs/start/coming-from-wix/)[Coming from Lovable or Builder.io](/docs/start/coming-from-ai-builders/)Studio[Overview](/docs/studio/)[The desktop app](/docs/studio/desktop/)The workspace[Overview](/docs/studio/interface/)[Welcome screen](/docs/studio/interface/welcome-screen/)[Editors and views](/docs/studio/interface/modes/)[The canvas](/docs/studio/interface/canvas/)[Documents and panes](/docs/studio/interface/tabs/)[Quick Access](/docs/studio/interface/quick-access/)[Keyboard shortcuts](/docs/studio/interface/shortcuts/)[Preferences](/docs/studio/interface/preferences/)[Languages](/docs/studio/interface/languages/)[Problems and progress](/docs/studio/interface/problems-and-progress/)[Commands](/docs/studio/interface/commands/)Projects[Overview](/docs/studio/projects/)[Create a project](/docs/studio/projects/create/)[Pages, layouts, components](/docs/studio/projects/pages-layouts-components/)[The Content workspace](/docs/studio/projects/browse/)[Starter templates](/docs/studio/projects/starters/)[Media](/docs/studio/projects/media/)[Content types](/docs/studio/projects/content-types/)[Project settings](/docs/studio/projects/settings/)[Dependencies and imports](/docs/studio/projects/dependencies/)Edit mode[Overview](/docs/studio/editing/)[Writing and formatting](/docs/studio/editing/writing/)[Slash commands](/docs/studio/editing/slash-commands/)[Frontmatter and 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architecture[Overview](/docs/framework/site/)[project.json](/docs/framework/site/project-json/)[Routing](/docs/framework/site/routing/)[Layouts](/docs/framework/site/layouts/)[Content collections](/docs/framework/site/content-collections/)[Jx Markdown](/docs/framework/site/jx-markdown/)[Obsidian vault as content](/docs/framework/site/obsidian-vault/)[Relationships](/docs/framework/site/relationships/)[SEO and metadata](/docs/framework/site/seo/)[Locales and languages](/docs/framework/site/i18n/)[Images](/docs/framework/site/images/)[Redirects](/docs/framework/site/redirects/)[Feeds](/docs/framework/site/feeds/)[Site search](/docs/framework/site/search/)[Build output and adapters](/docs/framework/site/deployment/)How compilation works[Overview](/docs/framework/build/)[The dev server](/docs/framework/build/dev-server/)[CLI commands](/docs/framework/build/cli/)Working with agents[Overview](/docs/framework/agents/)[Authoring rules for 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guestbook](/docs/extending/extensions/tutorial-guestbook/)[First-party extensions](/docs/extending/extensions/first-party/)Embedding[Overview](/docs/extending/embedding/)[Hosting the Studio assets](/docs/extending/embedding/hosting/)[Writing a platform adapter](/docs/extending/embedding/platform-adapter/)[The backend protocol](/docs/extending/embedding/backend-protocol/)[Dev server internals](/docs/extending/embedding/dev-server/)[Embedding the runtime in your app](/docs/extending/embedding/runtime-host/)[Writing assistant tools](/docs/extending/embedding/assistant-harness/)UI kit[The Jx UI kit](/docs/extending/ui-kit/)Reference[Protocol routes](/docs/extending/reference/studio-routes/)[Implementation status](/docs/extending/reference/implementation-status/)[Spec changelog](/docs/extending/reference/spec-changelog/)[Standards alignment](/docs/extending/reference/standards/)Contributing[Working in the monorepo](/docs/extending/contributing/monorepo/)[Contributing to these 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