> ## Documentation Index
> Fetch the complete documentation index at: https://superdoc-caio-pizzol-docs-ai-core-preset.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Underline extension

export const SourceCodeLink = ({extension, path}) => {
  const githubPath = path || `packages/super-editor/src/editors/v1/extensions/${extension.toLowerCase()}`;
  const githubUrl = `https://github.com/superdoc-dev/superdoc/tree/main/${githubPath}`;
  return <div>
      <p>
        <a href={githubUrl} target="_blank" rel="noopener noreferrer">
          View on GitHub →
        </a>
      </p>
    </div>;
};

export const SuperDocEditor = ({html = '<p>Start editing...</p>', height = '400px', maxHeight = '400px', onReady = null, showExport = true, customButtons = null}) => {
  const [ready, setReady] = useState(false);
  const editorRef = useRef(null);
  const containerIdRef = useRef(`editor-${Math.random().toString(36).substr(2, 9)}`);
  const DEV_DIST_URL = 'http://localhost:9094/dist';
  const UNPKG_DIST_URL = 'https://unpkg.com/superdoc@latest/dist';
  const getBaseUrl = async () => {
    const isDev = typeof window !== 'undefined' && window.location.hostname === 'localhost';
    if (isDev) {
      try {
        const res = await fetch(`${DEV_DIST_URL}/superdoc.min.js`, {
          method: 'HEAD'
        });
        if (res.ok) {
          console.info('[SuperDoc Docs] Using local build from', DEV_DIST_URL);
          return DEV_DIST_URL;
        }
        console.warn('[SuperDoc Docs] Local dev server returned', res.status, '- falling back to unpkg');
      } catch (err) {
        console.warn('[SuperDoc Docs] Local dev server not reachable: falling back to unpkg.', 'Run `pnpm dev:docs` from the repo root to use your local build.', err.message);
      }
    }
    return UNPKG_DIST_URL;
  };
  const ensureStyle = baseUrl => {
    const styleHref = `${baseUrl}/style.css`;
    if (document.querySelector(`link[href="${styleHref}"]`)) return;
    const link = document.createElement('link');
    link.rel = 'stylesheet';
    link.href = styleHref;
    document.head.appendChild(link);
  };
  const loadSuperDoc = baseUrl => {
    if (window.SuperDoc) return Promise.resolve();
    const scriptSrc = `${baseUrl}/superdoc.min.js`;
    const existingScript = document.querySelector(`script[src="${scriptSrc}"]`);
    if (existingScript) {
      if (window.SuperDoc) return Promise.resolve();
      return new Promise((resolve, reject) => {
        existingScript.addEventListener('load', resolve, {
          once: true
        });
        existingScript.addEventListener('error', reject, {
          once: true
        });
      });
    }
    return new Promise((resolve, reject) => {
      const script = document.createElement('script');
      script.src = scriptSrc;
      script.onload = resolve;
      script.onerror = reject;
      document.body.appendChild(script);
    });
  };
  const initEditor = () => {
    setTimeout(() => {
      if (!window.SuperDoc) return;
      if (!document.getElementById(containerIdRef.current)) return;
      if (editorRef.current) return;
      editorRef.current = new window.SuperDoc({
        selector: `#${containerIdRef.current}`,
        html,
        rulers: true,
        contained: true,
        onReady: () => {
          setReady(true);
          if (onReady) onReady(editorRef.current);
        }
      });
    }, 100);
  };
  useEffect(() => {
    let cancelled = false;
    const boot = async () => {
      try {
        const baseUrl = await getBaseUrl();
        ensureStyle(baseUrl);
        await loadSuperDoc(baseUrl);
        if (!cancelled) initEditor();
      } catch (error) {
        console.error('Failed to boot SuperDoc:', error);
      }
    };
    boot();
    return () => {
      cancelled = true;
      editorRef.current?.destroy?.();
      editorRef.current = null;
    };
  }, []);
  const exportDocx = () => {
    if (editorRef.current?.export) {
      editorRef.current.export();
    }
  };
  return <div className="border rounded-lg bg-white overflow-hidden">
      {ready && (showExport || customButtons) && <div className="px-3 py-2 bg-gray-50 border-b">
          {customButtons && <div className="space-y-1 mb-2">
              {customButtons.map((row, rowIndex) => <div key={rowIndex} className="flex gap-1">
                  {row.map((btn, i) => <button key={i} onClick={() => btn.onClick(editorRef.current)} className={btn.className || 'flex-1 px-2 py-1 bg-gray-100 text-gray-700 text-xs rounded hover:bg-gray-200'}>
                      {btn.label}
                    </button>)}
                </div>)}
            </div>}
          {showExport && <div className="text-right">
              <button onClick={exportDocx} className="px-3 py-1 bg-blue-500 text-white text-xs rounded hover:bg-blue-600">
                Export DOCX
              </button>
            </div>}
        </div>}
      <div id={containerIdRef.current} style={{
    height,
    maxHeight,
    paddingLeft: '5px'
  }} />
      <style jsx>{`
        #${containerIdRef.current} .superdoc__layers {
          max-width: 660px !important;
        }
        #${containerIdRef.current} .super-editor {
          max-width: 100% !important;
          width: 100% !important;
          color: #000;
        }
        #${containerIdRef.current} .editor-element {
          width: 100% !important;
          min-width: unset !important;
          transform: none !important;
        }
        #${containerIdRef.current} .editor-element {
          h1,
          h2,
          h3,
          h4,
          h5,
          strong {
            color: #000;
          }
        }
      `}</style>
    </div>;
};

Draw attention with underlined text.

Traditional emphasis technique, automatically applied to links.

<SuperDocEditor
  html={`<p><br/><br/><u>Important:</u> Underlines traditionally indicate hyperlinks on the web.<br/><br/>In documents, use underlines to <u>emphasize key points</u> or <u>indicate blank fields</u>.</p>`}
  height="250px"
  customButtons={[
[
  {
    label: 'Toggle Underline',
    onClick: (superdoc) => {
      const editor = superdoc?.activeEditor || superdoc?.editor
      if (!editor?.commands) return
      
      editor.commands.toggleUnderline()
    }
  },
  {
    label: 'Set Underline',
    onClick: (superdoc) => {
      const editor = superdoc?.activeEditor || superdoc?.editor
      if (!editor?.commands) return
      
      editor.commands.setUnderline()
    }
  },
  {
    label: 'Unset Underline',
    onClick: (superdoc) => {
      const editor = superdoc?.activeEditor || superdoc?.editor
      if (!editor?.commands) return
      
      editor.commands.unsetUnderline()
    }
  }
]
]}
/>

## OOXML Structure

```xml theme={null}
<w:r>
  <w:rPr>
    <w:u w:val="single"/>
  </w:rPr>
  <w:t>Underlined text</w:t>
</w:r>
```

## Use case

* **Legal documents** - Emphasize terms and conditions
* **Forms** - Indicate fill-in areas: \_\_\_\_\_\_\_\_\_\_\_\_\_
* **Headings** - Alternative to bold
* **Links** - Automatic with hyperlinks
* **Emphasis** - Triple emphasis with bold + italic + underline

## Options

Configure the extension behavior:

<ParamField path="htmlAttributes" type="Object" default="{}">
  HTML attributes for underline elements
</ParamField>

## Attributes

Mark attributes that can be set and retrieved:

<ParamField path="underlineType" type="UnderlineConfig" default="single">
  Style of underline
</ParamField>

<ParamField path="underlineColor" type="string">
  Color of the underline (hex color value)
</ParamField>

## Commands

### `setUnderline`

Apply underline formatting

**Example:**

<CodeGroup>
  ```javascript Usage theme={null}
  editor.commands.setUnderline()
  ```

  ```javascript Full Example theme={null}
  import { SuperDoc } from 'superdoc';
  import 'superdoc/style.css';

  const superdoc = new SuperDoc({
    selector: '#editor',
    document: yourFile,
    onReady: (superdoc) => {
      const editor = superdoc.activeEditor;
      editor.commands.setUnderline();
    },
  });
  ```
</CodeGroup>

**Returns:** `Function` Command

### `unsetUnderline`

Remove underline formatting

**Example:**

<CodeGroup>
  ```javascript Usage theme={null}
  editor.commands.unsetUnderline()
  ```

  ```javascript Full Example theme={null}
  import { SuperDoc } from 'superdoc';
  import 'superdoc/style.css';

  const superdoc = new SuperDoc({
    selector: '#editor',
    document: yourFile,
    onReady: (superdoc) => {
      const editor = superdoc.activeEditor;
      editor.commands.unsetUnderline();
    },
  });
  ```
</CodeGroup>

**Returns:** `Function` Command

### `toggleUnderline`

Toggle underline formatting

**Example:**

<CodeGroup>
  ```javascript Usage theme={null}
  editor.commands.toggleUnderline()
  ```

  ```javascript Full Example theme={null}
  import { SuperDoc } from 'superdoc';
  import 'superdoc/style.css';

  const superdoc = new SuperDoc({
    selector: '#editor',
    document: yourFile,
    onReady: (superdoc) => {
      const editor = superdoc.activeEditor;
      editor.commands.toggleUnderline();
    },
  });
  ```
</CodeGroup>

**Returns:** `Function` Command

## Keyboard shortcuts

| Command           | Shortcut   | Description                             |
| ----------------- | ---------- | --------------------------------------- |
| toggleUnderline() | `⌘/Ctrl-u` | Toggle underline formatting             |
| toggleUnderline() | `⌘/Ctrl-U` | Toggle underline formatting (uppercase) |

## Types

### `UnderlineConfig`

Underline style configuration

<Expandable title="Properties">
  <ResponseField name="value" type="any | any | any | any | any | any" required>
    Style variant
  </ResponseField>
</Expandable>

## Source code

<SourceCodeLink path="packages/super-editor/src/editors/v1/extensions/underline/underline.js" />