Affixing Header 

Create an affixing header that behaves normally as a user navigates down a page, but reveals itself naturally when a user scrolls or drags upwards. Inspired by iOS Safari, Medium, and others. See an example implementation to see what it’s about. Works on desktop and mobile browsers.

Usage

The module is ESM-only and exports a single default affixingHeader function:

affixingHeader( element, options )

element HTMLElement

The DOM element to which the affixing behavior should be attached. Must be a single HTMLElement (e.g., the result of document.querySelector or document.getElementById), not a NodeList.

options object { classNameAffixed?: string; classNameAffixing?: string; useSticky?: boolean }

Optional options for customizing the behavior of the affixing header:

• { classNameAffixed: string } will add the specified class to the header when it is affixed (i.e. when it has been scrolled up)
• { classNameAffixing: string } will add the specified class to the header when it is in the process of affixing (i.e. when the user has started scrolling up and the header is moving into view)
• { useSticky: true } will cause the module to use position: sticky (instead of position: fixed) when affixing the header on scrolling up

affixingHeader return value

affixingHeader function (element: HTMLElement) => () => void

The affixingHeader function returns a cleanup function that takes no arguments and is used to remove listeners and cleanup the affixing behavior.

Dependencies

This package uses onscrolling, a requestAnimationFrame-based, performant, mobile-friendly scroll event handler, to listen for page scrolls, but has no other dependencies.

Compatibility

This module is ESM-only and takes advantage of modern JS language features. It includes code to ensure it won’t throw errors in non-browser environments (e.g. node, workersd, deno, bun, etc.), where it will not do anything but also won’t break SSR. To make it compatible with non-ESM environments and older browsers, it must be transpiled.

Tests

Tests use vitest + happy-dom and can be run with yarn test.

TODO

• [ ] Add { scrollingParent: DOMElement } option for usage with scrollable elements other than scrollingDocument