purii/react-use-scrollspy

Flexible React Hook to automatically update navigation based on scroll position

react-use-scrollspy

Installation

react-use-scrollspy is a React Hook which requires React 16.8.0 or later.

// yarn
yarn add react-use-scrollspy
// or npm
npm i react-use-scrollspy --S

Usage

import useScrollSpy from 'react-use-scrollspy';
...
const activeSection = useScrollSpy({
  sectionElementRefs: [], // Array of References to DOM elements
});

Parameter	Default	Type	Description
defaultValue	0	int	Default value that is returned (optional)
offsetPx	0	int	Set offset (optional)
sectionElementRefs	[]	[Ref]	Array of Refs to observe (e.g. via React refs)
scrollingElement	window	Ref	Target of the scrolling (e.g. via React refs)) (optional)

with Refs

Use React refs for section elements like in the provided example.

import React, { useRef } from 'react';
import useScrollSpy from 'react-use-scrollspy';

const App = () => {

  const sectionRefs = [
    useRef(null),
    useRef(null),
    useRef(null),
  ];

  const activeSection = useScrollSpy({
    sectionElementRefs: sectionRefs,
    offsetPx: -80,
  });

  return (
    <nav className="App-navigation">
      <span className={activeSection === 0 ? "App-navigation-item App-navigation-item--active" : "App-navigation-item"}>Section 1</span>
      <span className={activeSection === 1 ? "App-navigation-item App-navigation-item--active" : "App-navigation-item"}>Section 2</span>
      <span className={activeSection === 2 ? "App-navigation-item App-navigation-item--active" : "App-navigation-item"}>Section 3</span>
    </nav>

    <section className="App-section" ref={sectionRefs[0]}>
      <h1>Section 1</h1>
    </section>
    <section className="App-section" ref={sectionRefs[1]}>
      <h1>Section 2</h1>
    </section>
    <section className="App-section" ref={sectionRefs[2]}>
      <h1>Section 3</h1>
    </section>
  )

react-use-scrollspy's Issues

ERROR in ./node_modules/react-use-scrollspy/lib/module/index.js 23:44 Module parse failed: Unexpected token (23:44) You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file

Minor Typo in README

README.md refers to the project as react-use-scrollyspy (note the y after scroll).

Typescript support

If I install the package on a typescript project, I get a warning:
Could not find a declaration file for module 'react-use-scrollspy'.

A declaration file should be added for typescript users

Check scroll position on re-render

Please add a useEffect call to the hook, so that the state is checked on re-renders. Especially on the first render. If you scroll to the last section and refresh the page the value is incorrect.

Variable number of sections

Any thoughts on what I can do if I have a variable number of sections to watch?

I can't run useRef in a loop (it's against the "rules of hooks").

Question: Custom scroll container?

Hi,

thanks for this hook. I was wondering if it would be possible to use it with a custom scroll container, e.g. a fixed height div with overflow: auto containing my list of sections. If so a quick example would be appreciated.

Cheers

Question: How to handle sections with small height at the bottom of the page?

First of all, thanks for the fantastic hook. Works like a charm! 👍

So, I have a page with dynamically generated sections with editable content, so the last section on the page sometimes has a small height say 100px and doesn't trigger the hook like it should be for other sections on the page
The hook works perfectly, even for the last section on the page, if it's height is large enough to be covered into the threshold value calculated using the offsetPx prop

import useScrollSpy from 'react-use-scrollspy';

// if I have 3 sections, and the height of the 3rd(last) section is small
// then activeSection value is never set to its index value i.e. 2
const activeSection = useScrollSpy({
  sectionElementRefs: sectionRefsArray,
  offsetPx: Y_OFFSET
});

Is there any way to handle this scenario?

Get activeSection by ID instead of number

Could you kindly advice on how to get the activeSection by sectionRefs id? Currently it is returning the index of the sectionRefs - 0, 1, 2 . I would need to return by sectionRefs.getAttribute(id) because the order of the section might differ than the navigation.

import React, { useRef } from 'react';
import useScrollSpy from 'react-use-scrollspy';

const App = () => {

const sectionRefs = [
useRef(null),
useRef(null),
useRef(null),
];

const activeSection = useScrollSpy({
sectionElementRefs: sectionRefs,
offsetPx: -80,
});

console.log(activeSection); ----> currently getting the index of the sectionRefs - 0, 1, 2 . Option to return by sectionRefs.getAttribute(id) because the order of the section might differ than the navigation.

return (

<span className={activeSection === "section-1" ? "active" : ""}>Section 1
<span className={activeSection === "section-2" ? "active" : ""}>Section 2
<span className={activeSection === "section-3"? "active" : ""}>Section 3

<section id="section-1" ref={sectionRefs[0]}>
  <h1>Section 1</h1>
</section>
<section id="section-2" ref={sectionRefs[1]}>
  <h1>Section 2</h1>
</section>
<section id="section-3" ref={sectionRefs[2]}>
  <h1>Section 3</h1>
</section>

)