react-scrollevents

React component for adding scroll events

About

The react-scrollevents package is a useful react component for any project requiring scroll interaction in its UI. Whether that be an animation triggered once scrolled to, infinite scroller, or scroll scrubbing, this component should make your job a lot easier. The component returns a handy callback allowing you to write your own scroll interactions without having to set it up yourself.

After implementing something similar in several other projects I figured it was time to set up a well-documented reusable component without any extra unneeded functionality. There are several great projects already available for this kind of thing including react-scrollmagic.

However, if you're looking for bare bones functionality or are not using the GSAP animation library react-scrollevents is a great option. If you simply need functionality for an infinite scroller, using IntersectionObserver may be a more performant option. Phong Lam gives a great overview of IntersectionObserver in his medium article Infinite Scroll’ing the right way.

live demo:

https://github.com/wjames111/react-scrollevents/examples

Examples source:

https://github.com/wjames111/react-scrollevents

Adding react-scrollevents

1. cd into your project and run

npm install --save react-scrollevents

1. import react-scrollevents component into a class component

import React, { Component } from 'react'
import ScrollEvents from 'react-scrollevents';
 
 
class App extends Component {
  constructor(props) {
    super(props)
 
  }
 
  render() {
    return (
      <div>
        <ScrollEvents />
      </div>
      )
  }
}

1. scrollEvents requires two parameters, a triggerElements prop and a onScrollYCallback prop.

triggerElements takes in a react ref, if multiple elements will be triggered please pass the refs into an array. While not advised, triggerElements will also take a className or id selector as a string.
onScrollYCallback requires a callback function that will be called during each trigger. This callback should accept three arguments, the index of the element triggered, the action (start or end), and the element's scroll progress.

import React, { Component } from 'react'
import ScrollEvents from 'react-scrollevents';
 
 
class App extends Component {
  constructor(props) {
    super(props);
 
    this.triggerOne = React.createRef();
    this.triggerTwo = React.createRef();
  }
 
  onScrollY(element, action, progress) {
    // trigger whatever action or animation here
    if (action == 'start' || action == 'end') {
      console.log(element + ' ' + action);
    } else {
      console.log(`${element} has been scrolled ${progress} percent`);
    }
  }
  }
 
  render() {
    return (
      <div>
        <div ref={this.triggerOne}>
        </div>
        <div ref={this.triggerTwo}>
        </div>
        <ScrollEvents
          triggerElements={[this.triggerOne, this.triggerTwo]}
          onScrollYCallback={this.onScrollY}
          />
      </div>
      )
  }
}

Additional Props

name	type	optional	default
triggerElements	array, react ref or string	no	required
onScrollYCallback	function	no	required
scrollContainer	react ref element or string	yes	window
isIndicator	boolean	yes	true
indicatorPlacement	string or number	yes	50%
indicatorStyles	object	yes	{}
isReplayable	boolean	yes	true
isDebounce	boolean	yes	false
debounceAmount	number	yes	15ms
customComponent	react component	yes	null

Optional Props Explained

scrollContainer is the element the event listener is attached to. By default, it's this will be the window object.
isIndicator, if set to true adds a pointer for debugging purposes. The default, is set to true.
indicatorPlacement defines where in the scrollContainer elements should be triggered.
indicatorStyles allows you to redefine what the pointer looks like. Useful for creating a custom sticky component.
isReplayable allows elements to be triggered more than once.
isDebounce determines if scroll event should use debounce.
debounceAmount will determine the length of the debounce in ms.
customComponent allows child components to be added inside the scrollEvents component.