simple-react-transition

simple-react-transition is a powerful library that allows you to compose complex UI animations using CSS transitions.

Install

npm install simple-react-transition

Simple Demo

Check out the code: https://codesandbox.io/s/simple-demo-s6vg5f

Advanced Demo

Check out the code: https://codesandbox.io/s/advanced-demo-w8dq4x

Basic Example

The API primarily consists of the Animations component.

You pass the Animations component an array of Renderers.

import { Renderer, Animations } from "simple-react-transition";
import { useState } from "react";

export default function App() {
  const [isVisible, setVisible] = useState(true);

  let renderers: Renderer[];
  if (isVisible) {
    renderers = [
      {
        key: "greeting",
        render: (animationStage) => {
          let opacity: number;
          if (animationStage === "mount" || animationStage === "remove") {
            opacity = 0;
          } else {
            opacity = 1;
          }
          const style = {
            opacity,
            transition: "all 1s" // Must be the same as `duration`
          };
          return <div style={style}>Hello!</div>;
        },
        duration: () => 1000 // Must be the same as the `transition` duration
      }
    ];
  } else {
    renderers = [];
  }

  return (
    <>
      <button onClick={() => setVisible(!isVisible)}>
        {isVisible ? "Hide" : "Show"} Greeting
      </button>
      <Animations renderers={renderers} />
    </>
  );
}

Code: https://codesandbox.io/s/basic-demo-7j9dwg

Learn About CSS Transitions: https://developer.mozilla.org/en-US/docs/Web/CSS/transition

API

AnimationStage

export type AnimationStage = 'mount' | 'add' | 'stable' | 'remove';

The AnimationStage type is passed to animated components so they can choose how to render themselves based on which stage of the animation cycle they are in.

mount

The mount animation stage occurs when the component has just been added to the DOM.

Typically during the mount stage, you render the component as the start of its adding animation.

add

The add stage occurs while the adding animation for the component is executing.

stable

The stable stage occurs when the component has finished its add animation, and also is not being removed from the DOM.

Components might spend most of their lifetime in stable.

The stable stage my be skipped if the component is removed before the add animation is completed.

remove

The remove stage occurs while the removal animation is executing.

After the remove stage completes, the component is removed from the DOM.

Typical Lifecycle:

mount -> add -> stable -> remove -> (removed)

Lifecycle if Removed Early

mount -> add -> remove -> (removed)

Renderer

export type Renderer = {
    key: string;
    render(stage: AnimationStage): React.ReactNode;
    duration(stage: 'add' | 'remove'): number;
};

The Renderer defines an element that should be rendered as part of an Animations group.

key

Similarly to a React key, uniquely identifies this renderer amongst its peers in the Animations.

render

Given an AnimationStage, renders the component that will be added to the DOM.

This component should typically also have key. While the key should be unique, it doesn't have to be the same as the renderer's key (although it often is).

duration

Defines how long the add and remove animation stages take, in milliseconds.

This should typically be the same duration as your CSS transitions.

You may define the same duration for the add and remove stages.

You may use a duration of 0 for one or both stages. If you use a duration of 0, the stage still occurs, but only for one frame.

Animations

function Animations({ renderers: Array<Renderer> }): JSX.Element;

This component takes an array of Renderers, and controls their AnimationStages to facilitate the appropriate rendering of the components such that animations are executed.

The first time an Animations is rendered, its renderers are rendered in stage stable. This ensures that animations are not executed when the component initially renders.

Swapping

When two components are scheduled to be added and removed at the same time, Animations will ensure that they do not flicker.

In the above example, the square that's being dragged by the user and the square that is static are two different components.

In the code below, see how DraggingSquare and StaticSquare transition in and out at the same time.

// Less relevants parts removed with "//..."
let renderers: Renderer[];
if (dragPosition !== null) {
    renderers = [
        {
            key: "dragging",
            render: (stage) => (
                <DraggingSquare
                    key="dragging"
                    stage={stage}
                    position={dragPosition}
                />
            ),
            duration: (stage) => (stage === "add" ? 250 : 1000)
        }
    ];
} else {
    renderers = [
        {
            key: "not dragging",
            render: (stage) => <StaticSquare key="not dragging" stage={stage} />,
            duration: (stage) => (stage === "add" ? 1000 : 0)
        }
    ];
}

function StaticSquare({ stage }: { stage: AnimationStage }) {
    let opacity = stage === "stable" ? 1 : 0;

    const style = {
        //...
        opacity
    };

    return <div style={style} />;
}

The first swap occurs when dragging starts and DraggingSquare appears immediately, and StaticSquare disappears immediately.

The second swap occurs when dragging ends and DraggingSquare begins its 250ms removal animation. Meanwhile, StaticSquare begins its 250ms adding animation. StaticSquare gains back its opacity when it becomes stable at the end of its adding animation. At the same time, DraggingSquare is removed.

See the full code: https://codesandbox.io/s/swap-demo-6h37h5