use-dom

name	use-dom
description	Use Expo DOM components to run web code in a webview on native and as-is on web. Migrate web code to native incrementally.
version	1.0.0
license	MIT

What are DOM Components?

DOM components allow web code to run verbatim in a webview on native platforms while rendering as-is on web. This enables using web-only libraries like recharts, react-syntax-highlighter, or any React web library in your Expo app without modification.

When to Use DOM Components

Use DOM components when you need:

• Web-only libraries — Charts (recharts, chart.js), syntax highlighters, rich text editors, or any library that depends on DOM APIs
• Migrating web code — Bring existing React web components to native without rewriting
• Complex HTML/CSS layouts — When CSS features aren't available in React Native
• iframes or embeds — Embedding external content that requires a browser context
• Canvas or WebGL — Web graphics APIs not available natively

When NOT to Use DOM Components

Avoid DOM components when:

• Native performance is critical — Webviews add overhead
• Simple UI — React Native components are more efficient for basic layouts
• Deep native integration — Use local modules instead for native APIs
• Layout routes — _layout files cannot be DOM components

Basic DOM Component

Create a new file with the 'use dom'; directive at the top:

// components/WebChart.tsx
'use dom';

export default function WebChart({ data }: { data: number[]; dom: import('expo/dom').DOMProps }) {
  return (
    <div style={{ padding: 20 }}>
      <h2>Chart Data</h2>
      <ul>
        {data.map((value, i) => (
          <li key={i}>{value}</li>
        ))}
      </ul>
    </div>
  );
}

Rules for DOM Components

1. Must have 'use dom'; directive at the top of the file
2. Single default export — One React component per file
3. Own file — Cannot be defined inline or combined with native components
4. Serializable props only — Strings, numbers, booleans, arrays, plain objects
5. Include CSS in the component file — DOM components run in isolated context

The dom Prop

Every DOM component receives a special dom prop for webview configuration. Always type it in your props:

'use dom';

interface Props {
  content: string;
  dom: import('expo/dom').DOMProps;
}

export default function MyComponent({ content }: Props) {
  return <div>{content}</div>;
}

Common dom Prop Options

// Disable body scrolling
<DOMComponent dom={{ scrollEnabled: false }} />

// Flow under the notch (disable safe area insets)
<DOMComponent dom={{ contentInsetAdjustmentBehavior: "never" }} />

// Control size manually
<DOMComponent dom={{ style: { width: 300, height: 400 } }} />

// Combine options
<DOMComponent
  dom={{
    scrollEnabled: false,
    contentInsetAdjustmentBehavior: "never",
    style: { width: '100%', height: 500 }
  }}
/>

Exposing Native Actions to the Webview

Pass async functions as props to expose native functionality to the DOM component:

// app/index.tsx (native)
import { Alert } from 'react-native';
import DOMComponent from '@/components/dom-component';

export default function Screen() {
  return (
    <DOMComponent
      showAlert={async (message: string) => {
        Alert.alert('From Web', message);
      }}
      saveData={async (data: { name: string; value: number }) => {
        // Save to native storage, database, etc.
        console.log('Saving:', data);
        return { success: true };
      }}
    />
  );
}

// components/dom-component.tsx
'use dom';

interface Props {
  showAlert: (message: string) => Promise<void>;
  saveData: (data: { name: string; value: number }) => Promise<{ success: boolean }>;
  dom?: import('expo/dom').DOMProps;
}

export default function DOMComponent({ showAlert, saveData }: Props) {
  const handleClick = async () => {
    await showAlert('Hello from the webview!');
    const result = await saveData({ name: 'test', value: 42 });
    console.log('Save result:', result);
  };

  return <button onClick={handleClick}>Trigger Native Action</button>;
}

Using Web Libraries

DOM components can use any web library:

// components/syntax-highlight.tsx
'use dom';

import SyntaxHighlighter from 'react-syntax-highlighter';
import { docco } from 'react-syntax-highlighter/dist/esm/styles/hljs';

interface Props {
  code: string;
  language: string;
  dom?: import('expo/dom').DOMProps;
}

export default function SyntaxHighlight({ code, language }: Props) {
  return (
    <SyntaxHighlighter language={language} style={docco}>
      {code}
    </SyntaxHighlighter>
  );
}

// components/chart.tsx
'use dom';

import { LineChart, Line, XAxis, YAxis, CartesianGrid, Tooltip } from 'recharts';

interface Props {
  data: Array<{ name: string; value: number }>;
  dom: import('expo/dom').DOMProps;
}

export default function Chart({ data }: Props) {
  return (
    <LineChart width={400} height={300} data={data}>
      <CartesianGrid strokeDasharray="3 3" />
      <XAxis dataKey="name" />
      <YAxis />
      <Tooltip />
      <Line type="monotone" dataKey="value" stroke="#8884d8" />
    </LineChart>
  );
}

CSS in DOM Components

CSS imports must be in the DOM component file since they run in isolated context:

// components/styled-component.tsx
'use dom';

import '@/styles.css'; // CSS file in same directory

export default function StyledComponent({ dom }: { dom: import('expo/dom').DOMProps }) {
  return (
    <div className="container">
      <h1 className="title">Styled Content</h1>
    </div>
  );
}

Or use inline styles / CSS-in-JS:

'use dom';

const styles = {
  container: {
    padding: 20,
    backgroundColor: '#f0f0f0',
  },
  title: {
    fontSize: 24,
    color: '#333',
  },
};

export default function StyledComponent({ dom }: { dom: import('expo/dom').DOMProps }) {
  return (
    <div style={styles.container}>
      <h1 style={styles.title}>Styled Content</h1>
    </div>
  );
}

Expo Router in DOM Components

The expo-router <Link /> component and router API work inside DOM components:

'use dom';

import { Link, useRouter } from 'expo-router';

export default function Navigation({ dom }: { dom: import('expo/dom').DOMProps }) {
  const router = useRouter();

  return (
    <nav>
      <Link href="/about">About</Link>
      <button onClick={() => router.push('/settings')}>Settings</button>
    </nav>
  );
}

Router APIs That Require Props

These hooks don't work directly in DOM components because they need synchronous access to native routing state:

• useLocalSearchParams()
• useGlobalSearchParams()
• usePathname()
• useSegments()
• useRootNavigation()
• useRootNavigationState()

Solution: Read these values in the native parent and pass as props:

// app/[id].tsx (native)
import { useLocalSearchParams, usePathname } from 'expo-router';
import DOMComponent from '@/components/dom-component';

export default function Screen() {
  const { id } = useLocalSearchParams();
  const pathname = usePathname();

  return <DOMComponent id={id as string} pathname={pathname} />;
}

// components/dom-component.tsx
'use dom';

interface Props {
  id: string;
  pathname: string;
  dom?: import('expo/dom').DOMProps;
}

export default function DOMComponent({ id, pathname }: Props) {
  return (
    <div>
      <p>Current ID: {id}</p>
      <p>Current Path: {pathname}</p>
    </div>
  );
}

Detecting DOM Environment

Check if code is running in a DOM component:

'use dom';

import { IS_DOM } from 'expo/dom';

export default function Component({ dom }: { dom?: import('expo/dom').DOMProps }) {
  return <div>{IS_DOM ? 'Running in DOM component' : 'Running natively'}</div>;
}

Assets

Prefer requiring assets instead of using the public directory:

'use dom';

// Good - bundled with the component
const logo = require('../assets/logo.png');

export default function Component({ dom }: { dom: import('expo/dom').DOMProps }) {
  return <img src={logo} alt="Logo" />;
}

Usage from Native Components

Import and use DOM components like regular components:

// app/index.tsx
import { View, Text } from 'react-native';
import WebChart from '@/components/web-chart';
import CodeBlock from '@/components/code-block';

export default function HomeScreen() {
  return (
    <View style={{ flex: 1 }}>
      <Text>Native content above</Text>

      <WebChart data={[10, 20, 30, 40, 50]} dom={{ style: { height: 300 } }} />

      <CodeBlock code="const x = 1;" language="javascript" dom={{ scrollEnabled: true }} />

      <Text>Native content below</Text>
    </View>
  );
}

Platform Behavior

Platform	Behavior
iOS	Rendered in WKWebView
Android	Rendered in WebView
Web	Rendered as-is (no webview wrapper)

On web, the dom prop is ignored since no webview is needed.

Tips

• DOM components hot reload during development
• Keep DOM components focused — don't put entire screens in webviews
• Use native components for navigation chrome, DOM components for specialized content
• Test on all platforms — web rendering may differ slightly from native webviews
• Large DOM components may impact performance — profile if needed
• The webview has its own JavaScript context — cannot directly share state with native