React Scrollama

React Scrollama is a simple library for scrollytelling in React, utilizing the IntersectionObserver. It's adapted from Russel Samora's Scrollama.

Some examples:

17 interactive visualization stories using React Scrollama for scrollytelling
Comment Tati a imprimé sa marque à Barbès by Fabien Casaleggio
The scramble to secure America’s voting machines by Beatrice Jin
Sex Diversity Among Grad Students is Stagnating by Jason Kao

Demo

A live demo lives here, presented at ReactNYC.

Basic step triggers	Sticky graphic on the side

Install

React Scrollama can be installed as an npm package:

$ npm install react-scrollama

Note: Version 2.2.0 removed the IntersectionObserver polyfill from the build. If you want cross-browser support, you should include it yourself.

Usage

A Scrollama component wraps a set of steps. Each Step component must wrap a DOM element (i.e. not just text).

<Scrollama onStepEnter={callback} offset={0.5}>
  <Step data={1}>
    <div>...</div>
  </Step>
  <Step data={2}>
    <div>...</div>
  </Step>
</Scrollama>

<Scrollama> provides an interface for listening in on scroll triggers like entering or exiting a step. (Here's a full list of available props.)

A basic example:

import React, { useState } from 'react';
import { Scrollama, Step } from 'react-scrollama';

const ScrollamaDemo = () => {
  const [currentStepIndex, setCurrentStepIndex] = useState(null);

  // This callback fires when a Step hits the offset threshold. It receives the
  // data prop of the step, which in this demo stores the index of the step.
  const onStepEnter = ({ data }) => {
    setCurrentStepIndex(data);
  };

  return (
    <div style={{ margin: '50vh 0', border: '2px dashed skyblue' }}>
      <div style={{ position: 'sticky', top: 0, border: '1px solid orchid' }}>
        I'm sticky. The current triggered step index is: {currentStepIndex}
      </div>
      <Scrollama offset={0.5} onStepEnter={onStepEnter} debug>
        {[1, 2, 3, 4].map((_, stepIndex) => (
          <Step data={stepIndex} key={stepIndex}>
            <div
              style={{
                margin: '50vh 0',
                border: '1px solid gray',
                opacity: currentStepIndex === stepIndex ? 1 : 0.2,
              }}
            >
              I'm a Scrollama Step of index {stepIndex}
            </div>
          </Step>
        ))}
      </Scrollama>
    </div>
  );
};

export default ScrollamaDemo;

API

React Scrollama components do not render into the DOM. They are meant to set up Intersection Observers on the elements inside the <Step> components. In the code above, only the <div> elements would show up in the DOM.

Scrollama

These are the props you can set on the Scrollama component itself:

Prop	Type	Default	Description
offset	number (from 0 to 1) or pixel value (e.g. "300px")	0.3	How far from the top of the viewport to trigger a step (as a proportion of view height)
threshold	number (greater than 1)	4	Granularity of the progress interval in pixels (smaller = more granular)
onStepEnter	function		Callback that fires when the top or bottom edge of a step enters the offset threshold.
onStepExit	function		Callback that fires when the top or bottom edge of a step exits the offset threshold.
onStepProgress	function		Callback that fires the progress a step has made through the threshold.
debug	boolean	false	Whether to show visual debugging tools.

The onStepEnter and onStepExit callbacks receive one argument, an object, with the following properties:

{
  element, // The DOM node of the step that was triggered
  data, // The data supplied to the step
  direction, // 'up' or 'down'
  entry, // the original `IntersectionObserver` entry
}

The onStepProgress callback receives one argument, an object, with the following properties:

{
  element, // The DOM node of the step that was triggered
  data, // The data supplied to the step
  progress, // The percent of completion of the step (0 to 1)
  direction, // 'up' or 'down'
  entry, // the original `IntersectionObserver` entry
}

To create a fixed graphic with text scrolling beside/over it, use position: sticky;. How to use position sticky.

Step

A Step element can contain one child, which must be a DOM element. To use a React component as the child node, it must be wrapped with a DOM element like <div>.

These are the props you can set on the Step component:

Prop	Type	Default	Description
data	any		Data to be given to <Scrollama> callbacks when step triggered.

You will also probably want to set a key prop on each Step if you're transforming an array of data into a list of Step elements (see Lists and Keys).

Thank you to everyone who made this possible!

• jsonkao
• maerzhase
• NicholasLYang
• jonesbp
• kennethormandy
• cedricdelpoux
• davidnmora
• jefffriesen
• paolocorti
• elbertwang3
• michaelgrotton
• jjrchrds
• goleary
• danieleguido
• Lane
• jkjustjoshing

Features roadmap

• Currently, there is no way to throttle/customize React Scrollama's resize listener 😢. We're working on this in #44.
• Fire previous step triggers if they were jumped

Lmk if you need these features ASAP.