Swup Scroll Plugin

A swup plugin for customizable smooth scrolling.

• Enable smooth scrolling
• Animate scroll position between page visits
• Animate scrolling to anchors
• Define a custom offset for scroll positions
• Handle nested scroll containers
• Emulate scroll target selector

Installation

Install the plugin from npm and import it into your bundle.

npm install @swup/scroll-plugin

importSwupScrollPluginfrom'@swup/scroll-plugin';

Or include the minified production file from a CDN:

<scriptsrc="https://unpkg.com/@swup/scroll-plugin@4"></script>

Usage

To run this plugin, include an instance in the swup options.

constswup=newSwup({plugins: [newSwupScrollPlugin()]});

Behavior

Scroll Plugin works out of the box for sites where the window is the main scroll container, scrolling back up on page visits and restoring the previous position on browser history visits.

Scroll containers

If your site has other scroll containers than the window, like overflowing divs, the plugin will happily restore their scroll positions as long as you let it know about those containers. You can either add the attribute [data-swup-scroll-container] to them or use the scrollContainers option to configure a custom selector.

Reset vs. restore

On each page navigation, the plugin will reset the scroll position to the top just like the browser would. On backword/forward history visits, it will restore the previous scroll position that was saved right before leaving the page.

You can customize when to reset vs. restore while clicking a link using the shouldResetScrollPosition option. A common use case would be a custom back button: clicking it would normally reset the scoll position to the top while users would expect it to restore the previous scroll position on the page the link points towards.

Options

doScrollingRightAway

doScrollingRightAway defines if swup is supposed to wait for the replace of the page to scroll to the top.

animateScroll

animateScroll defines whether the scroll animation is enabled or swup simply sets the scroll without animation instead. Passing true or false will enable or disable all scroll animations. For finer control, you can pass an object:

{animateScroll: {betweenPages: true,samePageWithHash: true,samePage: true}}

💡 We encourage you to respect user preferences when setting the animateScroll option:

// Using a simple boolean...{animateScroll: !window.matchMedia('(prefers-reduced-motion: reduce)').matches}// ...or this little monster, with full control over everything:{animateScroll: window.matchMedia('(prefers-reduced-motion: reduce)').matches ? false : {betweenPages: true,samePageWithHash: true,samePage: true}}

getAnchorElement

Customize how the scroll target is found on the page. Defaults to standard browser behavior (#id first, a[name] second).

{// Use a custom data attribute instead of idgetAnchorElement: (hash)=>{hash=hash.replace('#','')returndocument.querySelector(`[data-scroll-target="${hash}"]`)}}

markScrollTarget

Due to certain limitations of the History API, the :target CSS pseudo-class stops working on sites that push their own history entries, which includes any site using swup. Enabling this option provides an alternative way of styling the current target element.

Navigating to the URL /index.html#section2 will make the following element the target element:

<sectionid="section2">Example</section>

To highlight the current target element, use the data-swup-scroll-target attribute for styling:

[data-swup-scroll-target] {
outline:5px auto blue;
}

Offset

Offset to substract from the final scroll position, to account for fixed headers. Can be either a static number or a function that returns a value based on the scroll target. To apply differing offsets for vertical and horizontal scrolling, return an object with top and left properties.

{// Number: fixed offset in pxoffset: 30,// Object: fixed vertical and horizontal offset in pxoffset: {top: 30,left: 10},// Function: calculate offset before scrollingoffset: ()=>document.querySelector('#header').offsetHeight,// The scroll target and container are passed into the functionoffset: (scrollTarget,scrollContainer)=>target.offsetHeight*2,}

scrollContainers

Customize the selector string used for finding scroll containers other than the window. See the Scroll Containers section for an explanation of how the plugin deals with overflowing containers.

{// Always restore the scroll position of overflowing tables and sidebarsscrollContainers: '.overflowing-table, .overflowing-sidebar'}

shouldResetScrollPosition

Callback function that allows customizing the behavior when a link is clicked. Instead of scrolling back up on page visits, returning false here will instead restore the previous scroll position recorded for that page. See Reset vs. restore for an explanation and use cases.

{// Don't scroll back up for custom back-links, mimicking the browser back buttonshouldResetScrollPosition: (link)=>!link.matches('.backlink')}

Default options

newSwupScrollPlugin({doScrollingRightAway: false,animateScroll: {betweenPages: true,samePageWithHash: true,samePage: true},getAnchorElement: null,markScrollTarget: false,offset: 0,scrollContainers: `[data-swup-scroll-container]`,shouldResetScrollPosition: (link)=>true,scrollFunction: undefined});

Methods on the swup instance

Scroll Plugin adds the method scrollTo to the swup instance, which can be used for custom scrolling. The method accepts a scroll position in pixels and a boolean whether the scroll position should be animated:

// will animate the scroll position of the window to 2000pxswup.scrollTo(2000,true);

Hooks

The plugin adds two new hooks scroll:start and scroll:end :

swup.hooks.on('scroll:start',()=>console.log('Swup started scrolling'));swup.hooks.on('scroll:end',()=>console.log('Swup finished scrolling'));

Custom scroll function

You can overwrite the scroll function with your own implementation by passing it in as the scrollFunction option. This way, you gain full control over how you animate your scroll positions. Below is an example using GSAP'sScrollToPlugin.

Note that you are responsible for calling the start and end functions passed to the scroll function to let swup correctly trigger the scroll:start and scroll:end hooks.

importSwupfrom'swup';importSwupScrollPluginfrom'@swup/scroll-plugin';import{gsap}from'gsap';importScrollToPluginfrom'gsap/ScrollToPlugin';gsap.registerPlugin(ScrollToPlugin);/** * Use GSAP ScrollToPlugin for animated scrolling * @see https://greensock.com/docs/v3/Plugins/ScrollToPlugin */newSwup({plugins: [newSwupScrollPlugin({scrollFunction: (el,top,left,animate,start,end)=>{gsap.to(el,{duration: animate ? 0.6 : 0,ease: "power4.out",scrollTo: {y: top,x: left,autoKill: window.matchMedia("(hover: hover)").matches,onAutoKill: ()=>end(),},onStart: ()=>start(),onComplete: ()=>end(),});},}),]});