### Clone Repository and Run Examples

Source: https://github.com/reactjs/react-transition-group/blob/master/README.md

Instructions to clone the project repository and set up the development environment. This involves installing dependencies and running Storybook to view interactive examples.

```bash
git clone git@github.com:reactjs/react-transition-group.git

npm install

npm run storybook
```

--------------------------------

### Install TypeScript Definitions

Source: https://github.com/reactjs/react-transition-group/blob/master/README.md

Installs the TypeScript definitions for react-transition-group, enabling type checking and autocompletion in TypeScript projects. This is done via npm.

```bash
npm install @types/react-transition-group
```

--------------------------------

### React Component with CSSTransitionGroup

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

An example React component demonstrating the use of the older `CSSTransitionGroup` API to animate a list of items. It includes state management for the list and event handlers for adding/removing items.

```javascript
class TodoList extends React.Component {
  constructor(props) {
    super(props);
    this.state = {items: ['hello', 'world', 'click', 'me']};
    this.handleAdd = this.handleAdd.bind(this);
  }

  handleAdd() {
    const newItems = this.state.items.concat([
      prompt('Enter some text')
    ]);
    this.setState({items: newItems});
  }

  handleRemove(i) {
    let newItems = this.state.items.slice();
    newItems.splice(i, 1);
    this.setState({items: newItems});
  }

  render() {
    const items = this.state.items.map((item, i) => (
      <div key={i} onClick={() => this.handleRemove(i)}>
        {item}
      </div>
    ));

    return (
      <div>
        <button onClick={this.handleAdd}>Add Item</button>
        <CSSTransitionGroup
          transitionName="example"
          transitionEnterTimeout={500}
          transitionLeaveTimeout={300}>
          {items}
        </CSSTransitionGroup>
      </div>
    );
  }
}
```

--------------------------------

### Migrate CSSTransitionGroup to TransitionGroup

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Shows the initial step of migrating a React component by replacing `CSSTransitionGroup` with `TransitionGroup`. This change prepares the component for the newer animation API.

```diff
 render() {
   const items = this.state.items.map((item, i) => (
     <div key={i} onClick={() => this.handleRemove(i)}>
       {item}
     </div>
   ));

   return (
     <div>
       <button onClick={this.handleAdd}>Add Item</button>
-      <CSSTransitionGroup
-        transitionName="example"
-        transitionEnterTimeout={500}
-        transitionLeaveTimeout={300}>
+      <TransitionGroup>
         {items}
-      </CSSTransitionGroup>
+      </TransitionGroup>
     </div>
   )
 }
```

--------------------------------

### Use Custom FadeTransition Component

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Demonstrates how to use the custom `FadeTransition` component in place of direct `CSSTransition` usage. This refactoring makes the render method cleaner and centralizes transition configuration.

```diff
 render() {
   const items = this.state.items.map((item, i) => (
-    <CSSTransition
-      key={i}
-      classNames="example"
-      timeout={{ enter: 500, exit: 300 }}
-    >
+    <FadeTransition key={i}>
       <div onClick={() => this.handleRemove(i)}>
         {item}
       </div>
-    </CSSTransition>
+    </FadeTransition>
   ));

   return (
     <div>
       <button onClick={this.handleAdd}>Add Item</button>
       <TransitionGroup>
         {items}
       </TransitionGroup>
     </div>
   )
 }
```

--------------------------------

### Wrap Items with CSSTransition

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Illustrates how to wrap individual list items with the `CSSTransition` component within `TransitionGroup`. This applies the specified animations to each item as it enters or leaves the list.

```diff
 render() {
   const items = this.state.items.map((item, i) => (
+    <CSSTransition
+      key={i}
+      classNames="example"
+      timeout={{ enter: 500, exit: 300 }}
+    >
       <div onClick={() => this.handleRemove(i)}>
         {item}
       </div>
+    </CSSTransition>
   ));

   return (
     <div>
       <button onClick={this.handleAdd}>Add Item</button>
       <TransitionGroup>
         {items}
       </TransitionGroup>
     </div>
   )
 }
```

--------------------------------

### CSS Transitions for React Transition Group

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Defines the CSS classes required for entry and exit animations. It specifies opacity changes and transition durations for elements entering and leaving the DOM.

```css
.example-enter {
  opacity: 0.01;
}

.example-enter.example-enter-active {
  opacity: 1;
  transition: opacity 500ms ease-in;
}

.example-leave {
  opacity: 1;
}

.example-leave.example-leave-active {
  opacity: 0.01;
  transition: opacity 300ms ease-in;
}
```

--------------------------------

### Property Mappings: v1 to v2

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Details the property renames and changes required when migrating from react-transition-group v1 to v2. This includes changes to transition names, timeouts, and boolean flags.

```javascript
v1:
<CSSTransitionGroup transitionName="fade"
                  transitionEnterTimeout={500}
                  transitionLeaveTimeout={500}>
  {items}
</CSSTransitionGroup>

v2:
<TransitionGroup>
  <CSSTransition classNames="fade"
                 timeout={{ enter: 500, exit: 500 }}>
    {items}
  </CSSTransition>
</TransitionGroup>
```

```javascript
v1:
transitionName -> classNames
transitionEnterTimeout, transitionLeaveTimeout -> timeout={{ exit, enter }}
transitionAppear -> appear
transitionEnter -> enter
transitionLeave -> exit
```

--------------------------------

### Update CSS from leave to exit

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Demonstrates the necessary CSS class name changes for the migration. The `leave` prefix is updated to `exit` to align with the newer `CSSTransition` component's naming convention.

```diff
 .example-enter {
   opacity: 0.01;
 }

 .example-enter.example-enter-active {
   opacity: 1;
   transition: opacity 500ms ease-in;
 }

-.example-leave {
+.example-exit {
   opacity: 1;
 }

-.example-leave.example-leave-active {
+.example-exit.example-exit-active {
   opacity: 0.01;
   transition: opacity 300ms ease-in;
 }
```

--------------------------------

### Create Reusable FadeTransition Component

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Defines a custom React component, `FadeTransition`, that encapsulates the `CSSTransition` logic with predefined `classNames` and `timeout` props. This promotes code reuse and simplifies transition application.

```javascript
const FadeTransition = (props) => (
  <CSSTransition
    {...props}
    classNames="example"
    timeout={{ enter: 500, exit: 300 }}
  />
);
```

--------------------------------

### Use Lifecycle Callbacks for React Transition States

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

Child lifecycle methods have been removed in v2. To perform actions during transition state changes (enter, exit), use the new lifecycle callback props: `onEnter`, `onEntering`, `onEntered`, `onExit`, `onExiting`, and `onExited`. Each callback receives the DOM node of the transition component.

```jsx
<Transition
  {...props}
  onEnter={handleEnter}
  onEntering={handleEntering}
  onEntered={handleEntered}
  onExit={handleExit}
  onExiting={handleExiting}
  onExited={handleExited}
/>
```

--------------------------------

### Wrap TransitionGroup with Transition Components in React

Source: https://github.com/reactjs/react-transition-group/blob/master/Migration.md

In v2, `<TransitionGroup>` no longer manages transitions via custom child lifecycle methods. Instead, it requires children to be `<Transition>` components. Props intended for the transition must be passed through from the `<TransitionGroup>`'s children to the `<Transition>` component itself, often using a spread operator.

```jsx
const MyTransition = ({ children: child, ...props }) => (
  // NOTICE THE SPREAD! THIS IS REQUIRED!
  <Transition {...props}>
    {transitionState => React.cloneElement(child, {
      style: getStyleForTransitionState(transitionState)
    })}
  </Transition>
);

const MyList = () => (
  <TransitionGroup>
    {items.map(item => (
      <MyTransition>{item}</MyTransition>
    )}
  </TransitionGroup>
);
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.