Package Exports

react-spring

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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:

You can only animate native styles and props
If you use transforms make sure it's an array
Receiving components have to be "animated components"
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, 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 components as children, you pass 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 transitions.

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 style={{ margin: 0, padding: 0, width: '100%', height: '100%', backgroundColor: 'white' }}>
                <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>
        )
    }
}