Expose a disclosure button’s expanded state.
HTML: Keep aria-expanded synchronized with the controlled panel’s hidden state.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Example</title>
</head>
<body>
<button aria-expanded="false" aria-controls="panel">Options</button><div id="panel" hidden>Extra options</div>
<script>
const button=document.querySelector('button');
button.onclick=()=>{
const expanded=button.getAttribute('aria-expanded')==='true';
button.setAttribute('aria-expanded',String(!expanded));
document.querySelector('#panel').hidden=expanded;
};
</script>
</body>
</html>Expected output EXAMPLE
Click the “Options” button. The “button” element has aria-expanded set to “true”. The “#panel” element is visible. Click the “button” element. The “#panel” element is not visible.
Details
Save as example.html and open in a modern browser. The output describes browser behavior verified with DOM and interaction assertions. Keep aria-expanded synchronized with the controlled panel’s hidden state.
Tested on Ubuntu 24.04.5 LTS · · Chromium 141.0.7390.37 · libc6 2.39-0ubuntu8.9; Playwright 1.56.0
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
Chromium: open example.html; execute the published browser assertions- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
044e32c4b26e641d77e97cf8131b394dec41b629c91ded34c09c1402e22aaa1c- Dependencies
- libc6 2.39-0ubuntu8.9; Playwright 1.56.0
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
Expected output describes the rendered page. The standard-output record below is the browser test harness receipt; the additional assertions check the result and interactions.
Expose a disclosure button’s expanded state: browser checks passed.
Exit code: 0. Standard error: empty. Validation: Shape/content assertions. System-dependent values above are one recorded run.
Additional assertions that passed
Checks recorded by the test harness. Where Python assertions are shown, browser cases use Playwright and simulator cases may inspect pin transitions: result.stdout is captured output, work is the temporary directory, and Path is pathlib.Path. The harness also imports json and csv.
await page.get_by_role('button',name='Options').click()
assert await page.locator('button').get_attribute('aria-expanded')=='true'
assert await page.locator('#panel').is_visible()
await page.locator('button').click()
assert not await page.locator('#panel').is_visible()