Get scroll direction from IntersectionObserverEntry

[jfbrennan]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API

What specific section or headline is this issue about?

Intersection change callbacks

What information was incorrect, unhelpful, or incomplete?

That section says:

Each entry in the list of thresholds is an IntersectionObserverEntry object describing one threshold that was crossed; that is, each entry describes how much of a given element is intersecting with the root element, whether or not the element is considered to be intersecting or not, and the direction in which the transition occurred.

I don't believe "and the direction in which the transition occurred" is true. There's no explicit field that describes direction. I wish there was - that's what I came looking for - but I don't think that exists.

What did you expect to see?

I was hoping to find an example of getting the scroll direction from an IntersectionObserverEntry, but I don't believe there is an explicit field for that (despite the docs sort of alluding to it).

It would be nice if MDN included an example of how to do it. From what I've researched, it's possible by checking entry.boundingClientRect.<top|bottom|left|right> < 0 and entry.isIntersecting, but I don't yet have a clean reliable code to share.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

No response

MDN metadata

Page report details

• Folder: en-us/web/api/intersection_observer_api
• MDN URL: https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API
• GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/api/intersection_observer_api/index.md
• Last commit: 76717f7
• Document last modified: 2023-07-17T23:17:51.000Z