Repository: facebook/react
File: packages/react-dom-bindings/src/client/ReactInputSelection.js (JavaScript)

Code before:
    node.ownerDocument &&
    containsNode(node.ownerDocument.documentElement, node)
  );
}

function isSameOriginFrame(iframe) {
  try {
    // Accessing the contentDocument of a HTMLIframeElement can cause the browser
    // to throw, e.g. if it has a cross-origin src attribute.
    // Safari will show an error in the console when the access results in "Blocked a frame with origin". e.g:
    // iframe.contentDocument.defaultView;
    // A safety way is to access one of the cross origin properties: Window or Location
    // Which might result in "SecurityError" DOM Exception and it is compatible to Safari.
    // https://html.spec.whatwg.org/multipage/browsers.html#integration-with-idl

    return typeof iframe.contentWindow.location.href === 'string';
  } catch (err) {
    return false;
  }
}

function getActiveElementDeep(containerInfo) {
  let win = window;
  if (containerInfo?.ownerDocument?.defaultView) {
    win = containerInfo.ownerDocument.defaultView
  }
  let element = getActiveElement(win.document);
  while (element instanceof win.HTMLIFrameElement) {
    if (isSameOriginFrame(element)) {
      win = element.contentWindow;
    } else {
      return element;
    }
    element = getActiveElement(win.document);
  }
  return element;
}

/**
 * @ReactInputSelection: React input selection module. Based on Selection.js,
 * but modified to be suitable for react and has a couple of bug fixes (doesn't
 * assume buttons have range selections allowed).
 * Input selection module for React.
 */

/**
 * @hasSelectionCapabilities: we get the element types that support selection
 * from https://html.spec.whatwg.org/#do-not-apply, looking at `selectionStart`
 * and `selectionEnd` rows.
 */
export function hasSelectionCapabilities(elem) {

Review comment (suggestion):
Note that we try to minimize optional chaining in the runtime because of how it expands when transpiled, and this case does it twice. Maybe:

```js
let win = containerInfo?.ownerDocument?.defaultView ?? window;
```

Code after:
    node.ownerDocument &&
    containsNode(node.ownerDocument.documentElement, node)
  );
}

function isSameOriginFrame(iframe) {
  try {
    // Accessing the contentDocument of a HTMLIframeElement can cause the browser
    // to throw, e.g. if it has a cross-origin src attribute.
    // Safari will show an error in the console when the access results in "Blocked a frame with origin". e.g:
    // iframe.contentDocument.defaultView;
    // A safety way is to access one of the cross origin properties: Window or Location
    // Which might result in "SecurityError" DOM Exception and it is compatible to Safari.
    // https://html.spec.whatwg.org/multipage/browsers.html#integration-with-idl

    return typeof iframe.contentWindow.location.href === 'string';
  } catch (err) {
    return false;
  }
}

function getActiveElementDeep(containerInfo) {
  let win = containerInfo?.ownerDocument?.defaultView ?? window;
  let element = getActiveElement(win.document);
  while (element instanceof win.HTMLIFrameElement) {
    if (isSameOriginFrame(element)) {
      win = element.contentWindow;
    } else {
      return element;
    }
    element = getActiveElement(win.document);
  }
  return element;
}

/**
 * @ReactInputSelection: React input selection module. Based on Selection.js,
 * but modified to be suitable for react and has a couple of bug fixes (doesn't
 * assume buttons have range selections allowed).
 * Input selection module for React.
 */

/**
 * @hasSelectionCapabilities: we get the element types that support selection
 * from https://html.spec.whatwg.org/#do-not-apply, looking at `selectionStart`
 * and `selectionEnd` rows.
 */
export function hasSelectionCapabilities(elem) {
  const nodeName = elem && elem.nodeName && elem.nodeName.toLowerCase();
  return (
    nodeName &&