react-spring

What is react-spring?

react-spring is a spring-physics-based animation library for React applications. It allows developers to create fluid and natural animations with ease, leveraging the power of physics to create realistic motion. The library is highly flexible and can be used for a variety of animation needs, from simple transitions to complex interactive animations.

What are react-spring's main functionalities?

Basic Animations

This feature allows you to create basic animations such as fading in and out. The `useSpring` hook is used to define the animation properties, and the `animated` component is used to apply these properties to a React element.

```jsx
import React from 'react';
import { useSpring, animated } from 'react-spring';

function BasicAnimation() {
  const props = useSpring({
    to: { opacity: 1 },
    from: { opacity: 0 },
  });

  return <animated.div style={props}>I will fade in</animated.div>;
}

export default BasicAnimation;
```

Keyframe Animations

This feature allows you to create keyframe animations, where an element transitions through multiple states. The `to` property can be an async function that defines a sequence of animations.

```jsx
import React from 'react';
import { useSpring, animated } from 'react-spring';

function KeyframeAnimation() {
  const props = useSpring({
    from: { transform: 'translate3d(0,0,0)' },
    to: async (next) => {
      await next({ transform: 'translate3d(100px,0,0)' });
      await next({ transform: 'translate3d(0,0,0)' });
    },
  });

  return <animated.div style={props}>I will move</animated.div>;
}

export default KeyframeAnimation;
```

Gesture-based Animations

This feature allows you to create gesture-based animations, such as dragging. The `useDrag` hook from `react-use-gesture` is used in combination with `useSpring` to create a draggable element.

```jsx
import React from 'react';
import { useSpring, animated } from 'react-spring';
import { useDrag } from 'react-use-gesture';

function Draggable() {
  const [props, set] = useSpring(() => ({ x: 0, y: 0 }));
  const bind = useDrag(({ offset: [x, y] }) => set({ x, y }));

  return <animated.div {...bind()} style={{ ...props, width: 100, height: 100, background: 'lightblue' }} />;
}

export default Draggable;
```

Other packages similar to react-spring

framer-motion

Framer Motion is a popular animation library for React that provides a simple API for creating animations and gestures. It is known for its ease of use and powerful features, such as layout animations and shared element transitions. Compared to react-spring, Framer Motion is more focused on providing a high-level API for common animation tasks, while react-spring offers more flexibility and control over the animation physics.

react-transition-group

React Transition Group is a low-level animation library for React that provides more control over the transition states of components. It is often used for simple animations like fading, sliding, and collapsing. Compared to react-spring, React Transition Group is more focused on managing the lifecycle of animations and transitions, while react-spring provides more advanced physics-based animations.

react-move

React Move is an animation library for React that allows you to create complex animations using a declarative syntax. It is designed to work well with data-driven animations and provides a flexible API for creating custom animations. Compared to react-spring, React Move is more focused on data-driven animations and provides a different approach to defining animations using a declarative syntax.

README

npm install react-spring

Examples: Api demonstration | Super fast native rendering | Transitions

Why 🤔

React-spring is a wrapper around a cooked down fork of Facebooks animated. It is trying to bridge Chenglou's React-motion and animated as both have their pros and cons, but definitively could benefit from one another:

React-motion

• Declarative api that doesn't involve manual management of handles
• Performance can suffer because components are re-rendered every frame
• Can't interpolate between raw state as it doesn't know colors, paths, gradients, etc.

Animated

• Interpolates most web privimites, units and patterns
• Efficiently changes styles in the dom instead of re-rendering a component with fresh props frame by frame
• Managing and orchestrating handles (starting/stopping/waiting/cleaning) can become a real chore

This lib inherits React-motions api while you can feed it everything animated can interpolate. It also has support for animateds efficient native rendering.

Default rendering 🐎

Like React-motion by default we'll render the receiving component every frame as it gives you more freedom to animate whatever you like. In many situations this will be ok.

import { Spring } from 'react-spring'

const TRIANGLE = 'M20,380 L380,380 L380,380 L200,20 L20,380 Z'
const RECTANGLE = 'M20,20 L20,380 L380,380 L380,20 L20,20 Z'
const RED = '#c23369'
const GREEN = '#28d79f'

const Content = ({ toggle, color, opacity, scale, path, start, stop, end }) => (
    <div style={{ background: `linear-gradient(to bottom, ${start} ${stop}, ${end} 100%)` }}>
        <svg
            onClick={toggle}
            style={{ opacity, transform: `scale3d(${scale}, ${scale}, ${scale})` }}
            version="1.1"
            viewBox="0 0 400 400">
            <g fill={color} fillRule="evenodd">
                <path id="path-1" d={path} />
            </g>
        </svg>
    </div>
)

class App extends React.Component {
    state = { toggle: true }
    toggle = () => this.setState(state => ({ toggle: !state.toggle }))
    render() {
        const toggle = this.state.toggle
        return (
            <Spring
                // Default values, optional ...
                from={{ opacity: 0 }}
                // Will animate to ...
                to={{
                    // Can be numbers, colors, paths, degrees, percentages, ...
                    opacity: 1,
                    color: toggle ? RED : GREEN,
                    start: toggle ? RED : 'black',
                    end: toggle ? 'black' : GREEN,
                    stop: toggle ? '0%' : '50%',
                    scale: toggle ? 1 : 2,
                    path: toggle ? TRIANGLE : RECTANGLE,
                }}
                // You can finetune spring settings
                config={{ friction: 1, tension: 10 }}
                // All additional props will be spread over the child
                toggle={this.toggle}
                // Child as function/render-prop, receives interpolated values
                children={Content}
            />
        )
    }
}

Native rendering 🚀

If you need more performance then pass the native flag. Now your component will only render once and all updates will be sent straight to the dom without any React reconciliation passes.

Just be aware of the following conditions:

1. You can only animate native styles and props
2. If you use transforms make sure it's an array
3. Receiving components have to be "animated components"
4. The values you receive are opaque objects, not regular values

import { Spring, animated } from 'react-spring'

const Content = ({ toggle, fill, backgroundColor, transform, path }) => (
    <animated.div style={{ backgroundColor }}>
        <animated.svg style={{ transform, fill }} version="1.1" viewBox="0 0 400 400">
            <g fillRule="evenodd" onClick={toggle}>
                <animated.path id="path-1" d={path} />
            </g>
        </animated.svg>
    </animated.div>
)

class App extends React.Component {
    state = { toggle: true }
    toggle = () => this.setState(state => ({ toggle: !state.toggle }))
    render() {
        const toggle = this.state.toggle
        return (
            <Spring
                native
                from={{ fill: 'black' }}
                to={{
                    fill: toggle ? '#247BA0' : '#70C1B3',
                    backgroundColor: toggle ? '#B2DBBF' : '#F3FFBD',
                    transform: [{ rotate: toggle ? '0deg' : '180deg' }, { scale: toggle ? 0.6 : 1.5 }],
                    path: toggle ? TRIANGLE : RECTANGLE,
                }}
                toggle={this.toggle}
                children={Content}
            />
        )
    }
}

If you need to interpolate native styles, use animated.template. For instance, given that you receive startColor and endColor as animatable values you could do it like so:

const Content = ({ startColor, endColor }) => {
    const background = animated.template`linear-gradient(bottom ${startColor} 0%, ${endColor} 100%)`
    return (
        <animated.div style={{ background }}>
            ...
        </animated.div>
    )
)

Transitions ☔️

Use SpringTransition and pass in your keys. from denotes base styles, enter styles are applied when objects appear, leave styles are applied when objects disappear. You do not pass in components as children but rather functions that receive a style object. Keys and children have to match in their order! You can again use the native flag for direct dom animation.

import React, { PureComponent } from 'react'
import { SpringTransition, animated } from 'react-spring'

export default class AppContent extends PureComponent {
    state = { items: ['item1', 'item2', 'item3'] }

    componentDidMount() {
        setTimeout(() => this.setState({ items: ['item1', 'item2', 'item3', 'item4'] }), 2000)
        setTimeout(() => this.setState({ items: ['item1', 'item3', 'item4'] }), 4000)
    }
    
    render() {
        return (
            <ul>
                <SpringTransition
                    native
                    keys={this.state.items}
                    from={{ opacity: 0, color: 'black', height: 0 }}
                    enter={{ opacity: 1, color: 'red', height: 18 }}
                    leave={{ opacity: 0, color: 'blue', height: 0 }}>
                    {this.state.items.map(item => styles => (
                        <animated.li style={{ overflow: 'hidden', ...styles }}>{item}</animated.li>
                    ))}
                </SpringTransition>
            </ul>
        )
    }
}