un-used, saving for later

interface/src/use-prompt.js

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+import * as React from 'react';
+import { useBeforeUnload, unstable_useBlocker as useBlocker } from 'react-router-dom';
+
+// You can abstract `useBlocker` to use the browser's `window.confirm` dialog to
+// determine whether or not the user should navigate within the current origin.
+// `useBlocker` can also be used in conjunction with `useBeforeUnload` to
+// prevent navigation away from the current origin.
+//
+// IMPORTANT: There are edge cases with this behavior in which React Router
+// cannot reliably access the correct location in the history stack. In such
+// cases the user may attempt to stay on the page but the app navigates anyway,
+// or the app may stay on the correct page but the browser's history stack gets
+// out of whack. You should test your own implementation thoroughly to make sure
+// the tradeoffs are right for your users.
+export default function usePrompt(
+  message: string | null | undefined | false,
+  { beforeUnload }: { beforeUnload?: boolean } = {}
+) {
+  let blocker = useBlocker(
+    React.useCallback(() => (typeof message === 'string' ? !window.confirm(message) : false), [message])
+  );
+  let prevState = React.useRef(blocker.state);
+  React.useEffect(() => {
+    if (blocker.state === 'blocked') {
+      blocker.reset();
+    }
+    prevState.current = blocker.state;
+  }, [blocker]);
+
+  useBeforeUnload(
+    React.useCallback(
+      (event) => {
+        if (beforeUnload && typeof message === 'string') {
+          event.preventDefault();
+          event.returnValue = message;
+        }
+      },
+      [message, beforeUnload]
+    ),
+    { capture: true }
+  );
+}