Unmounting components

When working with animations in React, especially when mounting and unmounting components with transitions, useMountedValue() hook or MountedBlock HOC from React UI Animate is a powerful tool. It facilitates smooth transitions for components entering and leaving the DOM.

tip

Both useMountedValue() hook and HOC MountedBlock provide same result. The MountedBlock HOC is easier and better to use. Check MountedBlock.

Using useMountedValue()

Let's walk through an example where we have a component that toggles its visibility using state and applies animations when it mounts and unmounts.

import { useState } from 'react';
import { useMountedValue, animate } from 'react-ui-animate';

export default function App() {
  const [visible, setVisible] = useState(false);

  // useMountedValue hook manages the mounting and unmounting animations
  const open = useMountedValue(visible, {
    from: 0, // Initial state [visible = false]
    enter: 1, // State when mounting [visible = true]
    exit: 0, // State when unmounting [visible from true to false]
  });

  return (
    <div>
      <button onClick={() => setVisible(!visible)}>
        {visible ? 'Hide' : 'Show'}
      </button>

      {/* Conditional rendering based on mounted state */}
      {open(
        (animation, mounted) =>
          mounted && (
            <animate.div
              style={{
                width: 100,
                height: 100,
                backgroundColor: '#3399ff',
                borderRadius: 4,
                opacity: animation.value,
              }}
            />
          )
      )}
    </div>
  );
}

Explanation

1. State Management:

   • We start with a visible state variable (false initially) to toggle the visibility of our component.

2. useMountedValue Hook:

   • useMountedValue() hook takes visible as its first argument. This tells the hook whether the component should be mounted (true) or unmounted (false).

   • The second argument is an options object defining animation states:

     • from: Initial state when not mounted (0 typically means hidden).
     • enter: State when mounting (1 typically means fully visible).
     • exit: State when unmounting (back to 0, hidden).

3. Rendering Logic:

   • The open function returned by useMountedValue() accepts a callback function with parameters animation and mounted.

   • Inside the callback, mounted is a boolean indicating whether the component is currently mounted (true) or unmounted (false).

   • open() conditionally renders animate.div based on the mounted state. This ensures that transitions are applied only when the component is mounting or unmounting.

4. Component Interaction:

   • The button toggles the visible state, which in turn triggers the mounting/unmounting animations managed by useMountedValue().

Configuring Animation

To configure mounting and unmounting animations:

Adding config

We can configure the animation by passing it in config object inside the useMountedValue() hook. You can customize any spring or timing based animations or pass any built-in pre-defined animation from react-ui-animate

import { useMountedValue, AnimationConfigUtils } from 'react-ui-animate';

const open = useMountedValue(visible, {
  from: 0,
  enter: 1,
  exit: 0,
  config: AnimationConfigUtils.BOUNCE,
});

Here, AnimationConfigUtils.BOUNCE provides a predefined bouncing effect, ensuring a visually engaging transition.

Interpolating Animation Values

You can interpolate animation values to achieve complex animations. For example:

interpolate(animation.value, [0, 1], [0, 200]),

Example

Here is the full example about configuring animations for useMountedValue():

import { useState } from 'react';
import {
  useMountedValue,
  animate,
  AnimationConfigUtils,
  interpolate,
} from 'react-ui-animate';

export default function App() {
  const [visible, setVisible] = useState(false);

  const open = useMountedValue(visible, {
    from: 0,
    enter: 1,
    exit: 0,
    config: AnimationConfigUtils.BOUNCE,
  });

  return (
    <div>
      <button onClick={() => setVisible(!visible)}>
        {visible ? 'Hide' : 'Show'}
      </button>

      {open(
        (animation, mounted) =>
          mounted && (
            <animate.div
              style={{
                width: 100,
                height: 100,
                backgroundColor: '#3399ff',
                borderRadius: 4,
                opacity: animation.value,
                position: 'relative',
                left: interpolate(animation.value, [0, 1], [0, 200]),
              }}
            />
          )
      )}
    </div>
  );
}

Using MountedBlock HOC

MountedBlock is a higher-order component (HOC) that simplifies the process of mounting and unmounting components with animations. It is built using the useMountedValue hook and provides a more convenient way to handle the same logic.

import { useState } from 'react';
import {
  MountedBlock,
  animate,
  AnimationConfigUtils,
  interpolate,
} from 'react-ui-animate';

export default function App() {
  const [visible, setVisible] = useState(false);

  return (
    <div>
      <button onClick={() => setVisible(!visible)}>
        {visible ? 'Hide' : 'Show'}
      </button>

      <MountedBlock state={visible} config={AnimationConfigUtils.BOUNCE}>
        {(animation) => (
          <animate.div
            style={{
              width: 100,
              height: 100,
              backgroundColor: 'red',
              translateX: interpolate(animation.value, [0, 1], [0, 200]),
              opacity: 0.3,
            }}
          />
        )}
      </MountedBlock>
    </div>
  );
}

Explanation

1. State Management:

   • We start with a visible state variable (false initially) to toggle the visibility of our component.

2. Rendering Logic:

   • MountedBlock HOC wraps the animate.div component.
   • The state prop of MountedBlock is set to the visible state, indicating whether the component should be mounted (true) or unmounted (false).
   • The config prop allows for additional animation configuration.
   • The animate.div component is rendered with the specified styles and interpolated values based on the animation state.
   • The children as a function is passed with the argument of animated value, animating from 0 to 1.

Summary

Using useMountedValue and MountedBlock from React UI Animate allows developers to easily manage and customize mounting and unmounting animations in React applications. By defining animation states and configurations, such as duration, easing functions, and predefined animations, developers can create smooth and intuitive transitions that enhance user experience and interface dynamics. This approach ensures that animations are not only visually appealing but also responsive to user interactions, making applications more engaging and user-friendly.

What's Next ?

In the next section, we will look at Animation Modifiers.