rails-infinite-scroll-posts VS IntersectionObserver

create an infinite scrolling blog roll in rails with hotwire by Steve Polito

Source Code

You should only create the images (or set the src) for the images which are visible to the user. See our infinite scroll example for a naive implementation. More elaborated code might use the https://www.w3.org/TR/intersection-observer/.

I got a little curious on the statuses of these standards and went on a bit of searching.

> CSS contain (CSS Containment Module Level 2) - First published in 2019, still Editor's Draft[1]. Not supported by Safari/WebKit.

> CSS offset-path (Motion Path Module Level 1) - First published in 2015, still Editor's Draft[2]. Not supported by Safari/WebKit.

> CSS overflow-anchor (CSS Scroll Anchoring Module Level 1) - First published in 2020, still Editor's Draft[3]. Not supported by Safari/WebKit.

> Resolution media queries (dppx) - W3C Recommendation since 2012[4]. Not supported by Safari/WebKit.

> :focus-visible (Selectors Level 4) - First published in 2011, still Editor's Draft[5]. Not supported by Safari/WebKit.

- Touch Events - W3C Recommendation since 2013[6]. Supported on iOS 3.2 (2010). I assume the author meant Pointer Events[7] which became W3C recommendation since 2019, and supported on 13.2 (2019).

> BroadcastChannel - WHATWG Living Standard[8]. Blocked by privacy concern on WebKit side since 2020[9]. Initial support landed in WebKit trunk as of 2021-07.[10]

> beforeprint/afterprint - WHATWG Living Standard[11]. Supported by Safari/WebKit since 2019 (iOS 13).

> Regex Lookbehind - ECMAScript 2018[12]. Not supported by Safari/WebKit.

> scrollIntoView (CSSOM View Module) - First introduced in CSSOM View Module since 2011, still Editor's Draft[13]. Not supported by Safari/WebKit.

> Screen Orientation API - First committed in wc3/screen-orientation in 2012, still a W3C Working Draft[14]. Not supported by Safari/WebKit.

> Date and time input types - WHATWG Living Standard[15], partial support by Safari/WebKit since 2012 (iOS 5) but no week/min/max.

> Service Workers - W3C Candidate Recommendation since 2019[16]. Supported by Safari/WebKit since 2018 (iOS 14.5).

- AbortSignal - WHATWG Living Standard[17]. Supported by Safari/WebKit since 2018 (iOS 11.3)

- Intersection Observer - First published in 2017, still W3C Working Draft[18]. Supported by Safari/WebKit since 2019 (iOS 12.2).

- Client-side form validation - WHATWG Living Standard[19]. Supported by Safari/WebKit since 2017 (iOS 10.3).

[1]: https://drafts.csswg.org/css-contain/#contain-property

[2]: https://drafts.fxtf.org/motion/#offset-path-property

[3]: https://drafts.csswg.org/css-scroll-anchoring/#exclusion-api

[4]: https://www.w3.org/TR/css3-mediaqueries/#resolution

[5]: https://drafts.csswg.org/selectors-4/#the-focus-visible-pseu...

[6]: https://www.w3.org/TR/touch-events/

[7]: https://www.w3.org/TR/pointerevents/

[8]: https://html.spec.whatwg.org/multipage/web-messaging.html#br...

[9]: https://github.com/whatwg/html/issues/5803

[10]: https://bugs.webkit.org/show_bug.cgi?id=227924

[11]: https://html.spec.whatwg.org/multipage/timers-and-user-promp...

[12]: https://262.ecma-international.org/9.0/

[13]: https://drafts.csswg.org/cssom-view/#dom-element-scrollintov...

[14]: https://www.w3.org/TR/screen-orientation/

[15]: https://html.spec.whatwg.org/multipage/input.html#date-state...

[16]: https://www.w3.org/TR/service-workers/

[17]: https://dom.spec.whatwg.org/#abortsignal

[18]: https://www.w3.org/TR/intersection-observer/

[19]: https://html.spec.whatwg.org/multipage/forms.html#client-sid...

W3.Org

I've used https://github.com/w3c/IntersectionObserver/tree/main/polyfill in the past and it's pretty much just import and forget.

// app/javascript/controllers/infinite_scoll_controller.js import { Controller } from "stimulus" export default class extends Controller { static targets = ["scrollArea", "pagination"] connect() { this.createObserver() } createObserver() { const observer = new IntersectionObserver( entries => this.handleIntersect(entries), { // https://github.com/w3c/IntersectionObserver/issues/124#issuecomment-476026505 threshold: [0, 1.0], } ) observer.observe(this.scrollAreaTarget) } handleIntersect(entries) { entries.forEach(entry => { if (entry.isIntersecting) { this.loadMore() } }) } loadMore() { const next = this.paginationTarget.querySelector("[rel=next]") if (!next) { return } const href = next.href fetch(href, { headers: { Accept: "text/vnd.turbo-stream.html", }, }) .then(r => r.text()) .then(html => Turbo.renderStreamMessage(html)) .then(_ => history.replaceState(history.state, "", href)) } }

import { Controller } from "stimulus" export default class extends Controller { static targets = ["entry"] static values = { path: String, } connect() { this.createObserver(); } createObserver() { let observer; let options = { // https://github.com/w3c/IntersectionObserver/issues/124#issuecomment-476026505 threshold: [0, 1.0] }; observer = new IntersectionObserver(entries => this.handleIntersect(entries), options); observer.observe(this.entryTarget); } handleIntersect(entries) { entries.forEach(entry => { if (entry.isIntersecting) { // https://github.com/turbolinks/turbolinks/issues/219#issuecomment-376973429 history.replaceState(history.state, "", this.pathValue); } }); } }