vanillajs-browser-helpers/scrollParent.mjs

Collection of convenience code snippets (helpers) that aims to make it a little easier to work with vanilla JS in the browser

import isDOMChildNode from './isDOMChildNode';
import viewport from './viewport';
/**
 * Get the parent element that has scrolling
 *
 * @param elm - The element whose scroll parent is determined
 * @return The scroll parent or the viewport
 */
export default function scrollParent(elm) {
    const vp = viewport(elm);
    if (!isDOMChildNode(elm) || elm === vp) {
        return vp;
    }
    const { position: elmPosition } = getComputedStyle(elm);
    if (elmPosition === 'fixed') {
        return vp;
    }
    const noStaticParent = elmPosition === 'absolute';
    let parent = elm.parentElement;
    while (parent && parent !== document.body) {
        const { position, overflow, overflowX, overflowY } = getComputedStyle(parent);
        if (!(noStaticParent && position === 'static')
            && /(auto|scroll)/.test(overflow + overflowY + overflowX)) {
            return parent;
        }
        parent = parent.parentElement;
    }
    return vp;
}