scroll-padlock/src/get-element-index.js

Locks elements scroll handling scrollbar gaps and iOS Safari with CSS variables

import getElementParent from './get-element-parent.js';

/**
 * Gets a given element position (index) in the DOM tree (where 0 is first-child, 1 is second etc...)
 * @param {HTMLElement} element The given element to be checked
 * @returns {Number} The position of the given element in the DOM tree
 */
export default element => {
    const siblings = getElementParent(element)?.children ?? [];

    let count = 0;

    for (let i = 0, j = siblings.length; i < j; i++) {
        const sibling = siblings[i];

        if (sibling === element) {
            return count;
        }

        count++;
    }

    return count;
};