npm install react-spring

Examples: Interpolation | Native rendering | Reveals | List transitions | Staggered | TodoMVC | DragList

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 animations
• Covers most of the essentials (springs, lists, transitions, reveals, staggered animations)
• Performance can suffer because components are re-rendered every frame with fresh props
• Can't interpolate between raw state as it doesn't know colors, paths, gradients, etc.

Animated

• Interpolates most web privimites, units and patterns
• Efficiently writes to the dom directly instead of re-rendering components frame by frame
• Managing and orchestrating handles (starting/stopping/waiting/cleaning) can become a real chore
• Missing essential prototypes like mount/unmount transitions

So as you see, they're polar opposites and the strengths of one are the weaknesses of another. React-spring inherits React-motions api while you can feed it everything animated can interpolate. It also has support for animateds efficient native rendering.

Default rendering 🏎

(Demo)

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 App = ({ toggle }) => (
    <Spring
        // Default values, optional ...
        from={{ opacity: 0 }}
        // Will animate to ...
        to={{
            // Can be numbers, colors, paths, degrees, percentages, arrays, ...
            start: toggle ? '#abc' : 'rgb(10,20,30)',
            end: toggle ? 'seagreen' : 'rgba(0,0,0,0.5)',
            stop: toggle ? '0%' : '50%',
            scale: toggle ? 1 : 2,
            rotate: toggle ? '0deg' : '45deg',
            path: toggle
                ? 'M20,380 L380,380 L380,380 L200,20 L20,380 Z' 
                : 'M20,20 L20,380 L380,380 L380,20 L20,20 Z',
        }}>
        
        {({ color, scale, rotate, path, start, stop, end }) => (
            <div style={{ background: `linear-gradient(to bottom, ${start} ${stop}, ${end} 100%)` }}>
                <svg style={{ transform: `scale(${scale}) rotate(${rotate})` }}>
                    <g><path d={path} /></g>
                </svg>
            </div>
        )}
        
    </Spring>
)

Don't like the way render props wrap your code?

const Header = ({ children, ...styles }) => (
    <h1 style={styles}>
        {children}
    </h1>
)

const App = ({ color, children }) => (
    <Spring to={{ color }} render={Header}>
        {children}
    </Spring>
)

Et voilà! Now you render a animated version of the Header component! All props that Spring doesn't recognize as its own will be spread over the receiving component, including children if you use render instead. It's actually faster as well since the function isn't recreated on every prop-change.

Native rendering 🚀

(Demo)

Pass the native flag for more performance. The animations will now be applied directly to the dom through requestAnimationFrame and the component will only render when it receives new props. The flag is available for all primitives (Spring, SpringTransition & SpringTrail).

Just be aware of the following conditions:

1. It only animates standard styles and element props, the values you receive are opaque objects, not regular values
2. Receiving elements must be animated.[elementName], for instance div becomes animated.div
3. If you need to interpolate styles use the template string literal

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

const App = ({ toggle }) => (
    <Spring
        native
        from={{ fill: 'black' }}
        to={{
            rotate: toggle ? '0deg' : '180deg',
            scale: toggle ? 1 : 2,
            path: toggle ? TRIANGLE : RECTANGLE,
        }}>

        {({ rotate, scale, path }) => (
            <animated.svg style={{ transform: template`rotate(${rotate}) scale(${scale})` }}>
                <g><animated.path d={path} /></g>
            </animated.svg>
        )}

    </Spring>
)

Transitions 🌑🌒🌓🌔🌕

(Demo)

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. Keys and children have to match in their order!

import { SpringTransition } from 'react-spring'

const App = ({ items }) => (
    <ul>
        <SpringTransition
            keys={items.map(item => item.key)}
            from={{ opacity: 0, color: 'black', height: 0 }}
            enter={{ opacity: 1, color: 'red', height: 18 }}
            leave={{ opacity: 0, color: 'blue', height: 0 }}>
            {items.map(item => styles => <li style={styles}>{item.text}</li>)}
        </SpringTransition>
     </ul>
  )
}

You can use this prototype for two-state reveals, simply render a single child that you can switch out for another.

const App = ({ toggle }) => (
    <SpringTransition
        keys={toggle ? 'ComponentA' : 'ComponentB'} 
        from={{ opacity: 0 }} 
        enter={{ opacity: 1 }} 
        leave={{ opacity: 0 }}>
        {toggle ? ComponentA : ComponentB}
    </SpringTransition>
)

Trails/Staggered transitions 🐾🐾🐾

(Demo)

Create trailing animations by using SpringTrail. The api is similar to SpringTransition though it will assume your list is fixed. The items will interpolate in a staggered fashion, internally one spring follows the interpolated value of the previous one thereby creating a staggered chain.

import { SpringTrail } from 'react-spring'

const App = ({ items }) => (
    <SpringTrail from={{ opacity: 0 }} to={{ opacity: 1 }} keys={items.map(item => item.key)}>
        {items.map(item => styles => (
            <div style={styles}>
                {item.text}
            </div>
        ))}
    </SpringTrail>
)

API | Changelog