React: What is React 19 useFormStatus?

1import { useFormStatus } from "react-dom";
2
3function SubmitButton() {
4  const { pending, data, method, action } = useFormStatus();
5
6  return (
7    <button type="submit" disabled={pending}>
8      {pending ? "Submitting..." : "Submit"}
9    </button>
10  );
11}
12
13// Must be inside a <form>
14function MyForm() {
15  return (
16    <form action={submitAction}>
17      <input name="email" type="email" />
18      <SubmitButton />
19    </form>
20  );
21}

1function UploadForm() {
2  return (
3    <form action={uploadAction}>
4      <input type="file" name="file" />
5      <UploadButton />
6    </form>
7  );
8}
9
10function UploadButton() {
11  const { pending, data } = useFormStatus();
12  const fileName = data?.get("file")?.name;
13
14  return (
15    <button type="submit" disabled={pending}>
16      {pending ? `Uploading ${fileName}...` : "Upload"}
17    </button>
18  );
19}