@mapbox/scroll-restorer

Preserve the scroll state of document.scrollingElement while navigating programmatically through history states — that is, client-side routing.

Installation

npm install @mapbox/scroll-restorer

Usage

1. Invoke the start method when you would like to begin storing the browser's scroll position in history states, likely when your application mounts.
2. Invoke the stop method when you would like to stop the restoration of scroll position, likely when your application unmounts.

Have a look at an example using React Router.

API

start

scrollRestorer.start([options])

Starts tracking the user's scroll position.

options

autoRestore

Type: boolean. Default: true.

When true, scroll-restorer will attempt to restore the scroll position on each popstate event. Set this to false if you want to manually control the scroll position restoration (e.g. you may wish to call restoreScroll at a very specific point in your application's rendering lifecycle).

captureScrollDebounce

Type: number. Default: 50.

The number of milliseconds by which the scroll-capturing function should be debounced.

end

scrollRestorer.end()

End scroll-restorer's behavior.

getSavedScroll

scrollRestorer.getSavedScroll([input])

Returns the scroll position retrieved from window.history or an optional popstate event. When the autoRestore option of start is true, this method will be invoked automatically, so you only want to use it manually if you've set autoRestore to false.

input

Type: { state: Object }, either window.history or a popstate event. Default: window.history.

restoreScroll

scrollRestorer.restoreScroll([input, attempts])

Manually restore the scroll position for a given history state or popstate event.

When the autoRestore option of start is true, this method will be invoked automatically, so you only want to use it manually if you've set autoRestore to false.

input

Type: { state: Object }, either window.history or a popstate event. Default: window.history.

attempts

Type: number. Default: 5.

The number of times to attempt adjusting the scroll position. scroll-restorer might need to make multiple attempts if the saved scroll state refers to a position that is not yet available because content is still loading.

React & React Router Example

import React, {Component} from 'react';
import {HashRouter, Link, Route} from 'react-router-dom';
import scrollRestorer from '@mapbox/scroll-restorer';

class ScrollRestorerExample extends Component {
  componentDidMount() {
    // Initiate the scroll position restoration behavior.
    scrollRestorer.start();
  }

  componentWillUnmount() {
    // Cease the scroll position restoration behavior.
    scrollRestorer.stop();
  }

  getContent(numParagraphs) {
    const paragraphArr = new Array(numParagraphs).fill();

    return (
      <div>
        <h1>Here are {numParagraphs} paragraph elements, enjoy!</h1>
        {paragraphArr.map((_, index) => <p key={index}>Paragraph #{index}.</p>)}
      </div>
    );
  }

  render() {
    return (
      <HashRouter>
        <div>
          <nav style={{background: '#fff', position: 'fixed', top: 0, left: 0, width: '100%'}}>
            <Link to="/">Home</Link> &nbsp;
            <Link to="/page-a">Page A</Link> &nbsp;
            <Link to="/page-b">Page B</Link> &nbsp;
            <Link to="/page-c">Page C</Link>
          </nav>
          <main style={{marginTop: '40px'}}>
            <Route exact path="/" render={() => <h1>This is the home page.</h1>} />
            <Route exact path="/page-a" render={() => this.getContent(5)} />
            <Route exact path="/page-b" render={() => this.getContent(20)} />
            <Route exact path="/page-c" render={() => this.getContent(100)} />
          </main>
        </div>
      </HashRouter>
    );
  }
}

export default ScrollRestorerExample;

Influences

• delayed-scroll-restoration-polyfill
• scroll-behavior