1 files changed, 25 insertions, 0 deletions
diff --git a/popperjs/package/lib/dom-utils/contains.js.flow b/popperjs/package/lib/dom-utils/contains.js.flow
new file mode 100644
index 0000000..3164792
--- /dev/null
+++ b/popperjs/package/lib/dom-utils/contains.js.flow
@@ -0,0 +1,25 @@
+// @flow
+import { isShadowRoot } from './instanceOf';
+
+export default function contains(parent: Element, child: Element) {
+  const rootNode = child.getRootNode && child.getRootNode();
+
+  // First, attempt with faster native method
+  if (parent.contains(child)) {
+    return true;
+  }
+  // then fallback to custom implementation with Shadow DOM support
+  else if (rootNode && isShadowRoot(rootNode)) {
+    let next = child;
+    do {
+      if (next && parent.isSameNode(next)) {
+        return true;
+      }
+      // $FlowFixMe[prop-missing]: need a better way to handle this...
+      next = next.parentNode || next.host;
+    } while (next);
+  }
+
+  // Give up, the result is false
+  return false;
+}