react-scroll-parallax

React Scroll Parallax

Provides a React component and single passive scroll listener to add vertical scrolling based offsets to elements based on their position in the viewport. Works with universal (server-side rendered) React apps.

Examples

Some links demonstrating possible effects created with this lib:

• Example Site
• Parallax Testing
• CodePen Parallax
• CodePen Parallax Banner

Install

With npm

npm i react-scroll-parallax --save

or yarn

yarn add react-scroll-parallax

Usage

The <ParallaxProvider /> should wrap the component tree that contains all <Parallax /> components. This should be a top level component like <AppContainer />. For example:

import { ParallaxProvider } from 'react-scroll-parallax';

class AppContainer extends Component {
    render() {
        return (
            <ParallaxProvider>
                <App />
            </ParallaxProvider>
        );
    }
}

Import the Parallax component and use it anywhere within the provider like so:

import { Parallax } from 'react-scroll-parallax';

const ParallaxImage = () => (
    <Parallax
        className="custom-class"
        offsetYMax={20}
        offsetYMin={-20}
        slowerScrollRate
        tag="figure"
    >
        <Image src="/image.jpg" />
    </Parallax>
);

NOTE: Scroll state and positions of elements on the page are cached for performance reasons. This means that if the page height changes (most likely from images loading) after <Parallax /> components are mounted the controller won't properly determine when the elements are in view. To correct this you can call the parallaxController.update() method from any child component of the <ParallaxProvider /> via context. More details on how here: Parallax Controller Context.

<Parallax> Props

The following are all props that can be passed to the React <Parallax /> component:

Name	Type	Default	Description
className	String		Optionally pass additional class names to be added to the outer most parallax element.
disabled	Boolean	false	Determines if the component will have parallax offsets applied. If true parallax styles are completely removed from the element and it is no longer updated.
offsetXMax	Number or String	0	Maximum x offset in % or px. If no unit is passed percent is assumed. Percent is based on the elements width.
offsetXMin	Number or String	0	Minimum x offset in % or px. If no unit is passed percent is assumed. Percent is based on the elements width.
offsetYMax	Number or String	0	Maximum y offset in % or px. If no unit is passed percent is assumed. Percent is based on the elements height.
offsetYMin	Number or String	0	Minimum y offset in % or px. If no unit is passed percent is assumed. Percent is based on the elements height.
slowerScrollRate	Boolean	false	Internally swaps the min/max offset y values of the parallax component to give the appearance of moving faster or slower than the default rate of scroll.
tag	String	div	Optionally pass an element tag name to be applied to the outer most parallax element.

<ParallaxProvider>

The <ParallaxProvider /> component is meant to wrap a top level component in your application and is necessary to provide access though React's context API to the parallax controller. This component should only be used once in you app, for instance in an <AppContainer /> component that won't be mounted/unmounted during route changes. Like so:

const AppContainer = () => (
    <ParallaxProvider>
        <Router>
            <App />
        </Router>
    </ParallaxProvider>    
);

Parallax Controller Context

Access the Parallax Controller via React context in any components rendered within a <ParallaxProvider /> by defining the contextTypes like so:

class Foo extends Component {
    static contextTypes = {
        parallaxController: PropTypes.object.isRequired,
    };

    doSomething() {
        // do stuff with this.context.parallaxController
    }  
}

or for stateless functional components like:

const Bar = (props, context) => (
    // do stuff with context.parallaxController
);

Bar.contextTypes = {
    parallaxController: PropTypes.object.isRequired,
};

Available Methods

Access the following methods on parallaxController via context:

update()

Updates all cached attributes for parallax elements then updates their positions.

destroy()

Removes window scroll and resize listeners then resets all styles applied to parallax elements.

Example usage of context

The most common use case that would require access to the controller is dealing with images. Since the controller caches attributes for performance they will need to be updated with the correct values once the image loads. Here's an example of how you could do that with an <Image /> component:

class Image extends Component {
    static contextTypes = {
        parallaxController: PropTypes.object.isRequired,
    };

    handleLoad = () => {
        // updates cached values after image dimensions have loaded
        this.context.parallaxController.update();
    };

    render() {
        return <img src={this.props.src} onLoad={this.handleLoad} />;
    }
}

Browser Support

React scroll parallax should support the last two versions of all major browsers and has been tested on desktop Chrome, Firefox, Safari and Edge, as well as the following: iOS 9, iOS 10, Android 4 and IE11. If you encounter any errors for browsers that should be supported please post an issue.

Optimizations to Reduce Jank

React Scroll Parallax uses a single passive scroll listener (dependent on browser support) with the minimal amount of work done on the scroll event to prevent jank (calculations that cause layout, reflow and paint are cached initially and only updated when layout changes). Request animation frame is then used to decouple the scroll handler and further reduce jank. All offsets are applied with 3D transforms to utilize the GPU and prevent paints. If you have ideas to further optimize scrolling please PR or post an issue.

PSA

It's 2017 and you probably shouldn't be building parallax sites—but if you do (like I did) and you use this package try and use it responsibly. Keeping images small and optimized, reducing the number of moving elements in view and on the page, and disabling scroll effects on mobile devices should keep scrolling smooth.