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

Demo: https://codesandbox.io/embed/oln44nx8xq

React-spring is a wrapper around a cooked down fork of Facebooks animated. It is trying to bridge react-motion and animated in fact. React-motion is great but doesn't interpolate well, shifting from one state to another is hard as it can't deal with colors, gradients, paths, etc. Animated does that well, but the downside is manually having to manage animation-handles, doing stopping/cleaning chores.

This lib has a similar api as react-motion (Spring -> Motion, from -> defaultStyles, to -> styles) while you can feed it everything animated can take in.

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

Demo: https://codesandbox.io/s/882njxpz29

React-spring will re-render the receiving component on every frame. It is usually fine and gives you more freedom to animate whatever you like. If you need more performance supply the native flag. Now your component will only render once and all updates will efficiently be applied to it outside of Reacts render loop.

This has a few gotchas:

1. You can only animate styles!
2. The components that receive your styles have to be special, animated components. The styles are opaque objects, not regular styles!
3. If you use transforms, make sure it's an array

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

const DIV = animated.div
const SVG = animated.createAnimatedComponent('svg')

const Content = ({ toggle, color, backgroundColor, transform }) => (
    <DIV style={{ backgroundColor }}>
        <SVG style={{ transform }} version="1.1" viewBox="0 0 400 400">
            <g style={{ color }} fillRule="evenodd" onClick={toggle}>
                <path id="path-1" d="M20,380 L380,380 L380,380 L200,20 L20,380 Z" />
            </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
                native
                from={{ color: 'black' }}
                to={{
                    color: toggle ? '#247BA0' : '#70C1B3',
                    backgroundColor: toggle ? '#B2DBBF' : '#F3FFBD',
                    transform: [{ rotate: toggle ? '0deg' : '180deg' }, { scale: toggle ? 0.6 : 1.5 }],
                }}
                toggle={this.toggle}
                children={Content}
            />
        )
    }
}

By default you can use animated.div, animated.span and animated.img, you can create your own by calling: animated.createAnimatedComponent('h1') or whatever element you need.