[18] Switch code samples to createRoot (#4470)

* [18] Switch code samples to createRoot

* Feedback fixes

* Feedback updates

beta/src/pages/learn/add-react-to-a-website.md

@@ -74,11 +74,12 @@ function LikeButton() {
 
 ### Step 4: Add your React Component to the page {/*step-4-add-your-react-component-to-the-page*/}
 
-Lastly, add two lines to the bottom of **like_button.js**. These two lines of code find the `<div>` you added to your HTML in the first step and then display the "Like" button React component inside of it.
+Lastly, add three lines to the bottom of **like_button.js**. These three lines of code find the `<div>` you added to your HTML in the first step, create a React app with it, and then display the "Like" button React component inside of it.
 
 ```js
 const domContainer = document.getElementById('component-goes-here');
-ReactDOM.render(React.createElement(LikeButton), domContainer);
+const root = ReactDOM.createRoot(domContainer);
+root.render(React.createElement(LikeButton));
 ```
 
 **Congratulations! You have just rendered your first React component to your website!**
@@ -88,21 +89,21 @@ ReactDOM.render(React.createElement(LikeButton), domContainer);
 
 #### You can reuse components! {/*you-can-reuse-components*/}
 
-You might want to display a React component in multiple places on the same HTML page. This is most useful while React-powered parts of the page are isolated from each other. You can do this by calling `ReactDOM.render()` multiple times with multiple container elements.
+You might want to display a React component in multiple places on the same HTML page. This is most useful while React-powered parts of the page are isolated from each other. You can do this by calling `ReactDOM.createRoot()` multiple times with multiple container elements.
 
 1. In **index.html**, add an additional container element `<div id="component-goes-here-too"></div>`.
 2. In **like_button.js**, add an additional `ReactDOM.render()` for the new container element:
 
 ```js {6,7,8,9}
-ReactDOM.render(
-  React.createElement(LikeButton),
+const root1 = ReactDOM.createRoot(
   document.getElementById('component-goes-here')
 );
+root1.render(React.createElement(LikeButton));
 
-ReactDOM.render(
-  React.createElement(LikeButton),
+const root2 = ReactDOM.createRoot(
   document.getElementById('component-goes-here-too')
 );
+root2.render(React.createElement(LikeButton));
 ```
 
 Check out [an example that displays the "Like" button three times and passes some data to it](https://gist.github.com/rachelnabors/c0ea05cc33fbe75ad9bbf78e9044d7f8)!
@@ -157,8 +158,8 @@ Now you can use JSX in any `<script>` tag by adding `type="text/babel"` attribut
 
 ```jsx {1}
 <script type="text/babel">
-  ReactDOM.render(
-  <h1>Hello, world!</h1>, document.getElementById('root') );
+  const root = ReactDOM.createRoot(document.getElementById('root'));
+  root.render(<h1>Hello, world!</h1>);
 </script>
 ```
 

content/docs/add-react-to-a-website.md

@@ -77,14 +77,15 @@ Open **[this starter code](https://gist.github.com/gaearon/0b180827c190fe4fd98b4
 
 After **[the starter code](https://gist.github.com/gaearon/0b180827c190fe4fd98b4c7f570ea4a8/raw/b9157ce933c79a4559d2aa9ff3372668cce48de7/LikeButton.js)**, add two lines to the bottom of `like_button.js`:
 
-```js{3,4}
+```js{3,4,5}
 // ... the starter code you pasted ...
 
 const domContainer = document.querySelector('#like_button_container');
-ReactDOM.render(e(LikeButton), domContainer);
+const root = ReactDOM.createRoot(domContainer);
+root.render(e(LikeButton));
 ```
 
-These two lines of code find the `<div>` we added to our HTML in the first step, and then display our "Like" button React component inside of it.
+These three lines of code find the `<div>` we added to our HTML in the first step, create a React app with it, and then display our "Like" button React component inside of it.
 
 ### That's It! {#thats-it}
 

content/docs/addons-shallow-renderer.md

@@ -59,7 +59,7 @@ Shallow testing currently has some limitations, namely not supporting refs.
 
 You can think of the shallowRenderer as a "place" to render the component you're testing, and from which you can extract the component's output.
 
-`shallowRenderer.render()` is similar to [`ReactDOM.render()`](/docs/react-dom.html#render) but it doesn't require DOM and only renders a single level deep. This means you can test components isolated from how their children are implemented.
+`shallowRenderer.render()` is similar to [`root.render()`](/docs/react-dom-client.html#createroot) but it doesn't require DOM and only renders a single level deep. This means you can test components isolated from how their children are implemented.
 
 ### `shallowRenderer.getRenderOutput()` {#shallowrenderergetrenderoutput}
 

content/docs/addons-test-utils.md

@@ -89,7 +89,7 @@ Here is how we can test it:
 
 ```js{3,20-22,29-31}
 import React from 'react';
-import ReactDOM from 'react-dom';
+import ReactDOM from 'react-dom/client';
 import { act } from 'react-dom/test-utils';
 import Counter from './Counter';
 
@@ -108,7 +108,7 @@ afterEach(() => {
 it('can render and update a counter', () => {
   // Test first render and componentDidMount
   act(() => {
-    ReactDOM.render(<Counter />, container);
+    ReactDOM.createRoot(container).render(<Counter />);
   });
   const button = container.querySelector('button');
   const label = container.querySelector('p');
@@ -304,7 +304,7 @@ Render a React element into a detached DOM node in the document. **This function
 
 ```js
 const domContainer = document.createElement('div');
-ReactDOM.render(element, domContainer);
+ReactDOM.createRoot(domContainer).render(element);
 ```
 
 > Note:

content/docs/components-and-props.md

@@ -70,17 +70,15 @@ function Welcome(props) {
 }
 
 const element = <Welcome name="Sara" />;
-ReactDOM.render(
-  element,
-  document.getElementById('root')
-);
+const root = ReactDOM.createRoot(document.getElementById('root'));
+root.render(element);
 ```
 
 **[Try it on CodePen](https://codepen.io/gaearon/pen/YGYmEG?editors=1010)**
 
 Let's recap what happens in this example:
 
-1. We call `ReactDOM.render()` with the `<Welcome name="Sara" />` element.
+1. We call `root.render()` with the `<Welcome name="Sara" />` element.
 2. React calls the `Welcome` component with `{name: 'Sara'}` as the props.
 3. Our `Welcome` component returns a `<h1>Hello, Sara</h1>` element as the result.
 4. React DOM efficiently updates the DOM to match `<h1>Hello, Sara</h1>`.
@@ -111,11 +109,6 @@ function App() {
     </div>
   );
 }
-
-ReactDOM.render(
-  <App />,
-  document.getElementById('root')
-);
 ```
 
 **[Try it on CodePen](https://codepen.io/gaearon/pen/KgQKPr?editors=1010)**

content/docs/concurrent-mode-adoption.md

@@ -74,7 +74,7 @@ import ReactDOM from 'react-dom';
 //
 // You can opt into Concurrent Mode by writing:
 
-ReactDOM.unstable_createRoot(
+ReactDOM.createRoot(
   document.getElementById('root')
 ).render(<App />);
 ```

content/docs/forms.md

@@ -275,10 +275,10 @@ Specifying the `value` prop on a [controlled component](/docs/forms.html#control
 The following code demonstrates this. (The input is locked at first but becomes editable after a short delay.)
 
 ```javascript
-ReactDOM.render(<input value="hi" />, mountNode);
+ReactDOM.createRoot(mountNode).render(<input value="hi" />);
 
 setTimeout(function() {
-  ReactDOM.render(<input value={null} />, mountNode);
+  ReactDOM.createRoot(mountNode).render(<input value={null} />);
 }, 1000);
 
 ```

content/docs/handling-events.md

@@ -84,11 +84,6 @@ class Toggle extends React.Component {
     );
   }
 }
-
-ReactDOM.render(
-  <Toggle />,
-  document.getElementById('root')
-);
 ```
 
 [**Try it on CodePen**](https://codepen.io/gaearon/pen/xEmzGg?editors=0010)

content/docs/hello-world.md

@@ -8,11 +8,10 @@ next: introducing-jsx.html
 
 The smallest React example looks like this:
 
-```js
-ReactDOM.render(
-  <h1>Hello, world!</h1>,
-  document.getElementById('root')
-);
+```jsx
+ReactDOM
+  .createRoot(document.getElementById('root'))
+  .render(<h1>Hello, world!</h1>);
 ```
 
 It displays a heading saying "Hello, world!" on the page.

content/docs/hooks-faq.md

@@ -148,7 +148,7 @@ We'll test it using React DOM. To make sure that the behavior matches what happe
 
 ```js{3,20-22,29-31}
 import React from 'react';
-import ReactDOM from 'react-dom';
+import ReactDOM from 'react-dom/client';
 import { act } from 'react-dom/test-utils';
 import Counter from './Counter';
 
@@ -167,7 +167,7 @@ afterEach(() => {
 it('can render and update a counter', () => {
   // Test first render and effect
   act(() => {
-    ReactDOM.render(<Counter />, container);
+    ReactDOM.createRoot(container).render(<Counter />);
   });
   const button = container.querySelector('button');
   const label = container.querySelector('p');

content/docs/implementation-notes.md

@@ -32,10 +32,11 @@ The reconciler itself doesn't have a public API. [Renderers](/docs/codebase-over
 Let's consider the first time you mount a component:
 
 ```js
-ReactDOM.render(<App />, rootEl);
+const root = ReactDOM.createRoot(rootEl);
+root.render(<App />);
 ```
 
-React DOM will pass `<App />` along to the reconciler. Remember that `<App />` is a React element, that is, a description of *what* to render. You can think about it as a plain object:
+`root.render` will pass `<App />` along to the reconciler. Remember that `<App />` is a React element, that is, a description of *what* to render. You can think about it as a plain object:
 
 ```js
 console.log(<App />);
@@ -236,9 +237,9 @@ This is working but still far from how the reconciler is really implemented. The
 The key feature of React is that you can re-render everything, and it won't recreate the DOM or reset the state:
 
 ```js
-ReactDOM.render(<App />, rootEl);
+root.render(<App />);
 // Should reuse the existing DOM:
-ReactDOM.render(<App />, rootEl);
+root.render(<App />);
 ```
 
 However, our implementation above only knows how to mount the initial tree. It can't perform updates on it because it doesn't store all the necessary information, such as all the `publicInstance`s, or which DOM `node`s correspond to which components.
@@ -412,7 +413,7 @@ If you're struggling to imagine how an internal instance tree is structured in m
 
  <img src="../images/docs/implementation-notes-tree.png" width="500" style="max-width: 100%" alt="React DevTools tree" />
 
-To complete this refactoring, we will introduce a function that mounts a complete tree into a container node, just like `ReactDOM.render()`. It returns a public instance, also like `ReactDOM.render()`:
+To complete this refactoring, we will introduce a function that mounts a complete tree into a container node and a public instance:
 
 ```js
 function mountTree(element, containerNode) {

content/docs/integrating-with-other-libraries.md

@@ -190,9 +190,9 @@ class Chosen extends React.Component {
 
 ## Integrating with Other View Libraries {#integrating-with-other-view-libraries}
 
-React can be embedded into other applications thanks to the flexibility of [`ReactDOM.render()`](/docs/react-dom.html#render).
+React can be embedded into other applications thanks to the flexibility of [`createRoot()`](/docs/react-dom-client.html#createRoot).
 
-Although React is commonly used at startup to load a single root React component into the DOM, `ReactDOM.render()` can also be called multiple times for independent parts of the UI which can be as small as a button, or as large as an app.
+Although React is commonly used at startup to load a single root React component into the DOM, `root.render()` can also be called multiple times for independent parts of the UI which can be as small as a button, or as large as an app.
 
 In fact, this is exactly how React is used at Facebook. This lets us write applications in React piece by piece, and combine them with our existing server-generated templates and other client-side code.
 
@@ -216,15 +216,9 @@ function Button() {
   return <button id="btn">Say Hello</button>;
 }
 
-ReactDOM.render(
-  <Button />,
-  document.getElementById('container'),
-  function() {
-    $('#btn').click(function() {
-      alert('Hello!');
-    });
-  }
-);
+$('#btn').click(function() {
+  alert('Hello!');
+});
 ```
 
 From here you could start moving more logic into the component and begin adopting more common React practices. For example, in components it is best not to rely on IDs because the same component can be rendered multiple times. Instead, we will use the [React event system](/docs/handling-events.html) and register the click handler directly on the React `<button>` element:
@@ -240,44 +234,40 @@ function HelloButton() {
   }
   return <Button onClick={handleClick} />;
 }
-
-ReactDOM.render(
-  <HelloButton />,
-  document.getElementById('container')
-);
 ```
 
 [**Try it on CodePen**](https://codepen.io/gaearon/pen/RVKbvW?editors=1010)
 
-You can have as many such isolated components as you like, and use `ReactDOM.render()` to render them to different DOM containers. Gradually, as you convert more of your app to React, you will be able to combine them into larger components, and move some of the `ReactDOM.render()` calls up the hierarchy.
+You can have as many such isolated components as you like, and use `ReactDOM.createRoot()` to render them to different DOM containers. Gradually, as you convert more of your app to React, you will be able to combine them into larger components, and move some of the `ReactDOM.createRoot()` calls up the hierarchy.
 
 ### Embedding React in a Backbone View {#embedding-react-in-a-backbone-view}
 
 [Backbone](https://backbonejs.org/) views typically use HTML strings, or string-producing template functions, to create the content for their DOM elements. This process, too, can be replaced with rendering a React component.
 
-Below, we will create a Backbone view called `ParagraphView`. It will override Backbone's `render()` function to render a React `<Paragraph>` component into the DOM element provided by Backbone (`this.el`). Here, too, we are using [`ReactDOM.render()`](/docs/react-dom.html#render):
+Below, we will create a Backbone view called `ParagraphView`. It will override Backbone's `render()` function to render a React `<Paragraph>` component into the DOM element provided by Backbone (`this.el`). Here, too, we are using [`ReactDOM.createRoot()`](/docs/react-dom-client.html#createroot):
 
-```js{1,5,8,12}
+```js{1,5,8-9,13}
 function Paragraph(props) {
   return <p>{props.text}</p>;
 }
 
 const ParagraphView = Backbone.View.extend({
   render() {
     const text = this.model.get('text');
-    ReactDOM.render(<Paragraph text={text} />, this.el);
+    this.root = ReactDOM.createRoot(this.el);
+    this.root.render(<Paragraph text={text} />);
     return this;
   },
   remove() {
-    ReactDOM.unmountComponentAtNode(this.el);
+    this.root.unmount();
     Backbone.View.prototype.remove.call(this);
   }
 });
 ```
 
 [**Try it on CodePen**](https://codepen.io/gaearon/pen/gWgOYL?editors=0010)
 
-It is important that we also call `ReactDOM.unmountComponentAtNode()` in the `remove` method so that React unregisters event handlers and other resources associated with the component tree when it is detached.
+It is important that we also call `root.unmount()` in the `remove` method so that React unregisters event handlers and other resources associated with the component tree when it is detached.
 
 When a component is removed *from within* a React tree, the cleanup is performed automatically, but because we are removing the entire tree by hand, we must call this method.
 
@@ -428,10 +418,8 @@ function Example(props) {
 }
 
 const model = new Backbone.Model({ firstName: 'Frodo' });
-ReactDOM.render(
-  <Example model={model} />,
-  document.getElementById('root')
-);
+const root = ReactDOM.createRoot(document.getElementById('root'));
+root.render(<Example model={model} />);
 ```
 
 [**Try it on CodePen**](https://codepen.io/gaearon/pen/PmWwwa?editors=0010)

content/docs/introducing-jsx.md

@@ -35,11 +35,6 @@ In the example below, we declare a variable called `name` and then use it inside
 ```js{1,2}
 const name = 'Josh Perez';
 const element = <h1>Hello, {name}</h1>;
-
-ReactDOM.render(
-  element,
-  document.getElementById('root')
-);
 ```
 
 You can put any valid [JavaScript expression](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators#Expressions) inside the curly braces in JSX. For example, `2 + 2`, `user.firstName`, or `formatName(user)` are all valid JavaScript expressions.
@@ -61,11 +56,6 @@ const element = (
     Hello, {formatName(user)}!
   </h1>
 );
-
-ReactDOM.render(
-  element,
-  document.getElementById('root')
-);
 ```
 
 **[Try it on CodePen](https://codepen.io/gaearon/pen/PGEjdG?editors=1010)**