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README.md
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# Lit + Zustand Architecture # Lit-Only Architecture (No Build)
A modern, no-build web application architecture using Lit web components with Zustand state management and IndexedDB persistence. A minimal, no-build web application using only Lit web components with local state management.
> **Note:** This is the `lit-only` branch. For the full-featured version with Zustand state management and IndexedDB persistence, see the `main` branch.
## For TSX/React Developers ## For TSX/React Developers
If you're coming from React/TSX, here's how this architecture maps to familiar concepts: If you're coming from React/TSX, here's how this minimal architecture maps to familiar concepts:
| React/TSX Pattern | This Architecture | | React/TSX Pattern | This Architecture |
|-------------------|-------------------| |-------------------|-------------------|
| `useState` / `useReducer` | Zustand vanilla store | | `useState` | Lit's `static properties` with `state: true` |
| `useEffect` + state subscription | `StoreController` (ReactiveController) | | Props drilling | Property passing via `.prop=${value}` |
| Context API | Global Zustand store | | Custom events | `CustomEvent` with `bubbles: true` |
| `localStorage` / `sessionStorage` | IndexedDB via persist middleware |
| JSX | Lit's `html` tagged template literals | | JSX | Lit's `html` tagged template literals |
| CSS-in-JS / CSS Modules | Lit's `css` tagged template literals | | CSS-in-JS / CSS Modules | Lit's `css` tagged template literals |
| React Router | Simple route state in store | | React Router | Simple route state in root component |
| Build step (Vite/Webpack) | Import maps (no build!) | | Build step (Vite/Webpack) | Import maps (no build!) |
### Key Differences ### Key Differences
1. **No Virtual DOM**: Lit uses native Web Components with efficient DOM updates 1. **No Virtual DOM**: Lit uses native Web Components with efficient DOM updates
2. **No Build Step**: Import maps let you use npm packages directly from CDN 2. **No Build Step**: Import maps let you use npm packages directly from CDN
3. **Reactive Controllers**: Replace hooks - attach to component lifecycle 3. **Local State Only**: Each component manages its own state, parent manages shared state
4. **Tagged Templates**: Instead of JSX, use `html\`<div>...</div>\`` 4. **Event-Based Communication**: Child components emit events, parent handles them
5. **Tagged Templates**: Instead of JSX, use `html\`<div>...</div>\``
## Architecture Overview ## Architecture Overview
* **Lit-based web components** - Standards-based, framework-agnostic UI * **Lit-based web components** - Standards-based, framework-agnostic UI
* **No-build tooling** - Import maps only, no bundler required * **No-build tooling** - Import maps only, no bundler required
* **Zustand state management** - Lightweight, vanilla JS store * **Local state management** - Component properties and state
* **IndexedDB persistence** - Automatic state persistence with idb-keyval * **Event-driven** - CustomEvents for child-to-parent communication
## Project Structure
## Layout
``` ```
src/
store/
index.js ← zustand store definition
middleware/
persistence.js ← idb-keyval persist adapter
sync.js ← optional cross-tab broadcast
components/ components/
app-root.js app-root.js ← Root component with shared state
feature-a/ nav-bar.js ← Navigation component
feature-a.js ← Lit component page-home.js ← Home page component
feature-a.css ← adopted stylesheet or constructable page-items.js ← Items page component
controllers/ index.html ← Entry point with inline importmap
fetch.js ← ReactiveController for API calls README.md
3d.js ← optional Three/WebGPU controller tasks.md
lib/
idb.js ← thin idb-keyval wrapper/schema
index.html
importmap.json ← extracted importmap (referenced via <script src>)
``` ```
## Data Flow Diagrams ## Data Flow Pattern
### Component-to-Store Pattern ### Parent-to-Child (Props)
```mermaid ```javascript
sequenceDiagram // Parent passes data down
participant User html`<child-component .items=${this.items}></child-component>`
participant LitComponent
participant StoreController
participant ZustandStore
participant IndexedDB
User->>LitComponent: Click button // Child receives via properties
LitComponent->>ZustandStore: Call action (e.g., addItem) static properties = {
ZustandStore->>ZustandStore: Update state items: { type: Array }
ZustandStore->>IndexedDB: Persist (via middleware) }
ZustandStore->>StoreController: Notify subscribers
StoreController->>LitComponent: requestUpdate()
LitComponent->>LitComponent: Re-render
LitComponent->>User: Show updated UI
``` ```
### Store Subscription Pattern ### Child-to-Parent (Events)
```javascript
// Child emits event
this.dispatchEvent(new CustomEvent('add-item', {
detail: { item: newItem },
bubbles: true,
composed: true
}))
// Parent listens
html`<child-component @add-item=${(e) => this.handleAdd(e.detail.item)}></child-component>`
```
## State Management Pattern
```mermaid ```mermaid
graph TD graph TD
A[Zustand Store] -->|subscribe| B[StoreController] A[app-root] -->|.user, .items, .route| B[nav-bar]
B -->|selector function| C[Extract specific state] A -->|.user, .items| C[page-home]
C -->|value changed?| D{Compare} A -->|.items| D[page-items]
D -->|Yes| E[host.requestUpdate] B -->|@navigate event| A
D -->|No| F[Skip update] D -->|@add-item event| A
E --> G[Lit re-renders component] D -->|@remove-item event| A
style A fill:#f9f,stroke:#333,stroke-width:2px style A fill:#f9f,stroke:#333,stroke-width:2px
style B fill:#bbf,stroke:#333,stroke-width:2px style B fill:#bbf,stroke:#333,stroke-width:2px
style G fill:#bfb,stroke:#333,stroke-width:2px style C fill:#bfb,stroke:#333,stroke-width:2px
``` style D fill:#bfb,stroke:#333,stroke-width:2px
### Complete Mental Model
```
┌─────────────────────────────────────────┐
│ User Interaction │
└──────────────┬──────────────────────────┘
│ (events)
┌─────────────────────────────────────────┐
│ Lit Web Components │
│ - html`` templates (like JSX) │
│ - css`` styles (scoped) │
│ - Event handlers │
└──────────────┬──────────────────────────┘
│ (actions)
┌─────────────────────────────────────────┐
│ StoreController (glue layer) │
│ - ReactiveController interface │
│ - Subscribes to store │
│ - Triggers requestUpdate() │
└──────────────┬──────────────────────────┘
│ (selector)
┌─────────────────────────────────────────┐
│ Zustand Vanilla Store │
│ - Global state (like Context) │
│ - Actions (like reducers) │
│ - Subscriptions │
└──────────────┬──────────────────────────┘
│ (persist middleware)
┌─────────────────────────────────────────┐
│ IndexedDB (via idb-keyval) │
│ - Automatic persistence │
│ - Async storage │
└─────────────────────────────────────────┘
``` ```
## Quick Start Example ## Quick Start Example
### 1. Define Store (like Redux/Zustand) ### 1. Define a Component
```javascript
// store/index.js
import { createStore } from 'zustand/vanilla'
import { persist } from 'zustand/middleware'
export const store = createStore(
persist(
(set) => ({
count: 0,
increment: () => set(s => ({ count: s.count + 1 })),
}),
{ name: 'my-store' }
)
)
```
### 2. Create Component (like React component)
```javascript ```javascript
// components/counter.js // components/counter.js
import { LitElement, html, css } from 'lit' import { LitElement, html, css } from 'lit'
import { StoreController } from '../controllers/store.js'
import { store } from '../store/index.js'
class Counter extends LitElement { class Counter extends LitElement {
// Subscribe to store (like useSelector) static properties = {
#count = new StoreController(this, store, s => s.count) count: { type: Number, state: true }
}
constructor() {
super()
this.count = 0
}
static styles = css` static styles = css`
button { padding: 1rem; font-size: 1.2rem; } button { padding: 1rem; font-size: 1.2rem; }
@ -171,8 +116,8 @@ class Counter extends LitElement {
render() { render() {
return html` return html`
<div> <div>
<p>Count: ${this.#count.value}</p> <p>Count: ${this.count}</p>
<button @click=${() => store.getState().increment()}> <button @click=${() => this.count++}>
Increment Increment
</button> </button>
</div> </div>
@ -183,7 +128,7 @@ class Counter extends LitElement {
customElements.define('my-counter', Counter) customElements.define('my-counter', Counter)
``` ```
### 3. Use in HTML (no build step!) ### 2. Use in HTML (no build step!)
```html ```html
<!DOCTYPE html> <!DOCTYPE html>
@ -192,9 +137,7 @@ customElements.define('my-counter', Counter)
<script type="importmap"> <script type="importmap">
{ {
"imports": { "imports": {
"lit": "https://esm.sh/lit@3", "lit": "https://esm.sh/lit@3"
"zustand/vanilla": "https://esm.sh/zustand@5/vanilla",
"zustand/middleware": "https://esm.sh/zustand@5/middleware"
} }
} }
</script> </script>
@ -206,17 +149,88 @@ customElements.define('my-counter', Counter)
</html> </html>
``` ```
## Component Communication Patterns
### Pattern 1: Shared State in Root
```javascript
class AppRoot extends LitElement {
static properties = {
items: { type: Array, state: true }
}
constructor() {
super()
this.items = []
}
addItem(item) {
this.items = [...this.items, item]
}
render() {
return html`
<child-component
.items=${this.items}
@add=${(e) => this.addItem(e.detail.item)}
></child-component>
`
}
}
```
### Pattern 2: Local State in Component
```javascript
class MyComponent extends LitElement {
static properties = {
_draft: { type: String, state: true }
}
constructor() {
super()
this._draft = ''
}
render() {
return html`
<input
.value=${this._draft}
@input=${e => this._draft = e.target.value}
/>
`
}
}
```
## Benefits Over React/TSX ## Benefits Over React/TSX
**No build step** - Edit and refresh, instant feedback **No build step** - Edit and refresh, instant feedback
**Minimal dependencies** - Just Lit, nothing else
**Smaller bundle** - No framework runtime, just standards **Smaller bundle** - No framework runtime, just standards
**Better encapsulation** - Shadow DOM, scoped styles **Better encapsulation** - Shadow DOM, scoped styles
**Framework agnostic** - Works anywhere, even in React apps **Framework agnostic** - Works anywhere, even in React apps
**Future-proof** - Built on web standards **Future-proof** - Built on web standards
**Easy to learn** - Simple mental model, no complex state management
## When to Use This vs. Full Stack
### Use Lit-Only When:
- Building small to medium apps
- Don't need persistence
- State is simple and hierarchical
- Want maximum simplicity
### Use Full Stack (main branch) When:
- Need IndexedDB persistence
- Complex state shared across many components
- Need cross-tab synchronization
- Want time-travel debugging
- Building larger applications
## See Also ## See Also
- [tasks.md](./tasks.md) - Current issues and improvements - [tasks.md](./tasks.md) - Current issues and improvements
- [Lit Documentation](https://lit.dev) - [Lit Documentation](https://lit.dev)
- [Zustand Documentation](https://zustand.docs.pmnd.rs)
- [Web Components](https://developer.mozilla.org/en-US/docs/Web/Web_Components) - [Web Components](https://developer.mozilla.org/en-US/docs/Web/Web_Components)
- [Import Maps](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script/type/importmap)

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import { LitElement, html, css } from "lit"; import { LitElement, html, css } from "lit";
import { store} from "../store/index.js";
import { StoreController } from "../controllers/store.js";
import "./nav-bar.js"; import "./nav-bar.js";
import "./page-home.js"; import "./page-home.js";
import "./page-items.js"; import "./page-items.js";
class AppRoot extends LitElement { class AppRoot extends LitElement {
#hydrated = new StoreController(this, store, s => s._hydrated); static properties = {
#user = new StoreController(this, store, s => s.user); user: { type: Object, state: true },
#route = new StoreController(this, store, s => s.route); route: { type: String, state: true },
items: { type: Array, state: true }
};
constructor() {
super();
this.user = null;
this.route = 'home';
this.items = [];
}
static styles = css` static styles = css`
:host { :host {
display: block; display: block;
min-height: 100vh; min-height: 100vh;
} }
.loading {
display: grid;
place-items: center;
height: 100vh;
opacity: 0.4;
}
`; `;
render() { #navigate(route) {
if (!this.#hydrated.value) { this.route = route;
return html`<div class="loading">loading...</div>`;
} }
#addItem(item) {
this.items = [...this.items, item];
}
#removeItem(id) {
this.items = this.items.filter(i => i.id !== id);
}
render() {
return html` return html`
<nav-bar .user=${this.#user.value}></nav-bar> <nav-bar
.user=${this.user}
.route=${this.route}
@navigate=${(e) => this.#navigate(e.detail.route)}
></nav-bar>
<main>${this.#renderRoute()}</main> <main>${this.#renderRoute()}</main>
`; `;
} }
#renderRoute() { #renderRoute() {
switch (this.#route.value) { switch (this.route) {
case "home": return html`<page-home></page-home>`; case "home":
case "items": return html`<page-items></page-items>`; return html`<page-home .user=${this.user} .items=${this.items}></page-home>`;
default: return html`<page-home></page-home>`; case "items":
return html`<page-items
.items=${this.items}
@add-item=${(e) => this.#addItem(e.detail.item)}
@remove-item=${(e) => this.#removeItem(e.detail.id)}
></page-items>`;
default:
return html`<page-home .user=${this.user} .items=${this.items}></page-home>`;
} }
} }
} }

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// components/nav-bar.js // components/nav-bar.js
import { LitElement, html, css } from 'lit' import { LitElement, html, css } from 'lit'
import { store } from '../store/index.js'
import { StoreController } from '../controllers/store.js'
class NavBar extends LitElement { class NavBar extends LitElement {
#route = new StoreController(this, store, s => s.route)
static properties = { static properties = {
user: { type: Object } user: { type: Object },
route: { type: String }
} }
static styles = css` static styles = css`
@ -35,14 +32,18 @@ class NavBar extends LitElement {
#navigate(route, e) { #navigate(route, e) {
e.preventDefault() e.preventDefault()
store.getState().navigate(route) this.dispatchEvent(new CustomEvent('navigate', {
detail: { route },
bubbles: true,
composed: true
}))
} }
#link(route, label) { #link(route, label) {
return html` return html`
<a <a
href="/${route}" href="/${route}"
?active=${this.#route.value === route} ?active=${this.route === route}
@click=${(e) => this.#navigate(route, e)} @click=${(e) => this.#navigate(route, e)}
>${label}</a> >${label}</a>
` `

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// components/page-home.js // components/page-home.js
import { LitElement, html, css } from 'lit' import { LitElement, html, css } from 'lit'
import { store } from '../store/index.js'
import { StoreController } from '../controllers/store.js'
class PageHome extends LitElement { class PageHome extends LitElement {
#user = new StoreController(this, store, s => s.user) static properties = {
#items = new StoreController(this, store, s => s.items) user: { type: Object },
items: { type: Array }
}
static styles = css` static styles = css`
:host { display: block; padding: 2rem 1.5rem; } :host { display: block; padding: 2rem 1.5rem; }
@ -25,8 +25,8 @@ class PageHome extends LitElement {
` `
render() { render() {
const name = this.#user.value?.name ?? 'there' const name = this.user?.name ?? 'there'
const count = this.#items.value.length const count = this.items?.length ?? 0
return html` return html`
<h1>Hey, ${name}</h1> <h1>Hey, ${name}</h1>

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@ -1,16 +1,17 @@
// components/page-items.js // components/page-items.js
import { LitElement, html, css } from 'lit' import { LitElement, html, css } from 'lit'
import { store } from '../store/index.js'
import { StoreController } from '../controllers/store.js'
class PageItems extends LitElement { class PageItems extends LitElement {
#items = new StoreController(this, store, s => s.items)
static properties = { static properties = {
items: { type: Array },
_draft: { type: String, state: true } _draft: { type: String, state: true }
} }
_draft = '' constructor() {
super();
this.items = [];
this._draft = '';
}
static styles = css` static styles = css`
:host { display: block; padding: 2rem 1.5rem; } :host { display: block; padding: 2rem 1.5rem; }
@ -63,12 +64,22 @@ class PageItems extends LitElement {
#add() { #add() {
const name = this._draft.trim() const name = this._draft.trim()
if (!name) return if (!name) return
store.getState().addItem({ id: crypto.randomUUID(), name })
this.dispatchEvent(new CustomEvent('add-item', {
detail: { item: { id: crypto.randomUUID(), name } },
bubbles: true,
composed: true
}))
this._draft = '' this._draft = ''
} }
#remove(id) { #remove(id) {
store.getState().removeItem(id) this.dispatchEvent(new CustomEvent('remove-item', {
detail: { id },
bubbles: true,
composed: true
}))
} }
#onKeydown(e) { #onKeydown(e) {
@ -76,7 +87,7 @@ class PageItems extends LitElement {
} }
render() { render() {
const items = this.#items.value const items = this.items ?? []
return html` return html`
<h1>Items</h1> <h1>Items</h1>

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@ -1,23 +0,0 @@
export class StoreController {
constructor(host, store, selector) {
this.host = host
this.store = store
this.selector = selector
host.addController(this)
}
hostConnected() {
this._unsub = this.store.subscribe(
(state) => {
const next = this.selector(state)
if (next !== this.value) {
this.value = next
this.host.requestUpdate()
}
}
)
this.value = this.selector(this.store.getState())
}
hostDisconnected() { this._unsub?.() }
}

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@ -8,10 +8,7 @@
{ {
"imports": { "imports": {
"lit": "https://esm.sh/lit@3", "lit": "https://esm.sh/lit@3",
"lit/decorators.js": "https://esm.sh/lit@3/decorators.js", "lit/decorators.js": "https://esm.sh/lit@3/decorators.js"
"zustand/vanilla": "https://esm.sh/zustand@5/vanilla",
"zustand/middleware": "https://esm.sh/zustand@5/middleware",
"idb-keyval": "https://esm.sh/idb-keyval@6"
} }
} }
</script> </script>

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@ -1,33 +0,0 @@
// lib/idb.js
import { createStore, get, set, del, entries, clear } from 'idb-keyval'
// Named stores — each maps to a distinct IDBObjectStore
export const itemsStore = createStore('app-db', 'items')
export const userStore = createStore('app-db', 'user')
export const cacheStore = createStore('app-db', 'cache')
// Typed wrappers — keeps raw idb-keyval calls out of the rest of the app
// and gives you one place to add validation, logging, or migration logic
export const db = {
items: {
getAll: () => entries(itemsStore),
get: (id) => get(id, itemsStore),
set: (id, value) => set(id, value, itemsStore),
remove: (id) => del(id, itemsStore),
clear: () => clear(itemsStore),
},
user: {
get: () => get('user', userStore),
set: (value) => set('user', value, userStore),
clear: () => del('user', userStore),
},
cache: {
get: (key) => get(key, cacheStore),
set: (key, value) => set(key, value, cacheStore),
remove: (key) => del(key, cacheStore),
clear: () => clear(cacheStore),
}
}

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@ -1,42 +0,0 @@
import { createStore } from 'zustand/vanilla'
import { persist, createJSONStorage } from 'zustand/middleware'
import { get, set } from 'idb-keyval'
const storage = createJSONStorage(() => ({
getItem: async (name) => {
const value = await get(name)
return value ?? null
},
setItem: async (name, value) => {
await set(name, value)
},
removeItem: async (name) => {
await del(name)
},
}))
export const store = createStore(
persist(
(set, get) => ({
_hydrated: false,
user: null,
items: [],
route: 'home',
setUser: (user) => set({ user }),
addItem: (item) => set(s => ({ items: [...s.items, item] })),
removeItem: (id) => set(s => ({ items: s.items.filter(i => i.id !== id) })),
navigate: (route) => set({ route }),
}),
{
name: 'app-store',
storage,
onRehydrateStorage: () => {
return (state, error) => {
if (!error) {
store.setState({ _hydrated: true })
}
}
},
}
)
)

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@ -1,9 +0,0 @@
// store/middleware/persistence.js
import { db } from '../idb.js'
export const makeIdbStorage = (storeName) =>
createJSONStorage(() => ({
getItem: (name) => db[storeName].get(name),
setItem: (name, value) => db[storeName].set(name, value),
removeItem: (name) => db[storeName].remove(name),
}))