React IntersectionObserver

A simple wrapper around IntersectionObserver API to use it within react apps.

Installation

yarn

yarn add intersection-observer-react

npm

npm install intersection-observer-react

Basic Usage

See examples

• Scroll Spy
• Infinite Scroll

Children as function

  import { IntersectionObserver, Observable} from 'intersection-observer-react'
  
  render() {
    return (<IntersectionObserver>
      <Observable>
        { isVisible =>  isVisible && "I Am Visible"  } 
      </Observable>
    </IntersectionObserver>)
  }

OnEnter, OnLeave

  import React, { Component } from 'react';
  import { IntersectionObserver, Observable } from "intersection-observer-react";

  class YourComponent extends Component {
    constructor(props) {
      super(props);
      this.state = {
        isVisible: false
      }
    }
    onEnter = () => {
      this.setState({
        isVisible: true
      })
    }
    onLeave = () => {
      this.setState({
        isVisible: false
      })
    }
    render() {
      const { isVisible } = this.state;
      return (
        <IntersectionObserver>
          <Observable
           onEnter={this.onEnter}
           onLeave={this.onLeave}
          >
            { isVisible && "I am Visible" }
          </Observable>
        </IntersectionObserver>
      );
    }
  }

IntersectionObserver

Options

Same options as Intersection Observer API

var options = {
  root: document.querySelector('#scrollArea'),
  rootMargin: '0px',
  threshold: 1.0
}

root

The element that is used as the viewport for checking visiblity of the target. Defaults to the browser viewport if not specified or if null.

rootMargin

Margin around the root. Can have values similar to the CSS margin property, e.g. "10px 20px 30px 40px" (top, right, bottom, left). If the root element is specified, the values can be percentages. This set of values serves to grow or shrink each side of theroot element's bounding box before computing intersections. Defaults to all zeros.

threshold

Either a single number or an array of numbers which indicate at what percentage of the target's visibility the observer's callback should be executed. If you only want to detect when visibility passes the 50% mark, you can use a value of 0.5. If you want the callback run every time visibility passes another 25%, you would specify the array [0, 0.25, 0.5, 0.75, 1]. The default is 0 (meaning as soon as even one pixel is visible, the callback will be run). A value of 1.0 means that the threshold isn't considered passed until every pixel is visible.

Observable

Options

onceOnly

Will not be observed after the first onEnter is called.

<Observable onceOnly>
</Observable>