# React 18 Migration

[React 18](https://reactjs.org/blog/2022/03/29/react-v18.html) released with many new features, such as Concurrent React, Suspense, batched updates, and more.

Workspaces that upgrade to Nx 14 will be automatically migrated to React 18. This migration will also include an upgrade to React Router v6, if it is used in the workspace, as well as the removal of the deprecated `@testing-library/react-hook` package. Keep reading for more details.

**Note:** If you use npm v7/v8, you will need to use `npm install --force` after running `nx migrate 14.0.0` since `@testing-library/react-hook` does not support React 18. Don't worry, this package will be removed in the migration.

## New `react-dom/client` API

Nx will automatically update your applications to use the new `react-dom-/client` API.

From this:

```typescript jsx
import { StrictMode } from 'react';
import * as ReactDOM from 'react-dom';
import App from './app/app';

ReactDOM.render(
  <StrictMode>
    <App />
  </StrictMode>,
  document.getElementById('root')
);
```

To this:

```typescript jsx
import { StrictMode } from 'react';
import * as ReactDOM from 'react-dom/client';
import App from './app/app';

const root = ReactDOM.createRoot(
  document.getElementById('root') as HTMLElement
);
root.render(
  <StrictMode>
    <App />
  </StrictMode>
);
```

There might be additional changes needed for your code to be fully compatible with React 18. If you use `React.FC` type (which Nx does not use), then you will need to
update your component props to include `children` explicitly.

Before:

```typescript jsx
interface MyButtonProps {
  color: string;
}
```

After:

```typescript jsx
interface MyButtonProps {
  color: string;
  children?: React.ReactNode; // children is no longer implicitly provided by React.FC
}
```

For more information on React 18 migration, please see the [official guide](https://reactjs.org/blog/2022/03/08/react-18-upgrade-guide.html).

## React Router v6

In addition to the React 18 migration, Nx will also update your workspace to React Router v6 -- assuming you use React Router v5 previously.
There are breaking changes in React Router v6. Please refer to the official [v5 to v6 guide](https://reactrouter.com/docs/en/v6/upgrading/v5) for details.

We highly recommend teams to upgrade their workspace to v6, but if you choose to opt out and continue to use v5, then you will need to disable React strict mode. Navigation is broken in strict mode for React Router v5 due to a transition issue.

To disable strict mode, open your `main.tsx` file and remove `<Strict>` in your render function.

Before:

```typescript jsx
root.render(
  <Strict>
    <BrowserRouter>
      <App />
    </BrowserRouter>
  </Strict>
);
```

After (for React Router v5):

```typescript jsx
root.render(
  <BrowserRouter>
    <App />
  </BrowserRouter>
);
```

## `@testing-library/react-hook` is deprecated

The `@testing-library/react-hook` package provides a `renderHook` function to test custom hooks. Unfortunately, this package
does not support React 18, and has been deprecated. The good news is that `@testing-library/react` (RTL) now comes with its own
`renderHook` utility function since version 13.1.0.

Nx will migrate your code to import `renderHook` from `@testing-library/react` instead of the deprecated package. There are a couple of
utility functions missing from the RTL package: `waitForNextUpdate` and `waitForValueToChange`. If you use either of these
utility functions, try swapping them with `waitFor` instead.

If you continue to have issues after the migration, please open an issue on the RTL repo: https://github.com/testing-library/react-testing-library.