initialiseMenuWidths.js

const initialiseMenuWidths = (menuItem) => {
    const menuContents = menuItem.querySelector('.menu-contents');

    // Find the longest menu item
    const maxWidth = Math.max(
        ...Array.from(menuContents.querySelectorAll('.nav-content li')).map(
            (el) => el.offsetWidth
        )
    );

    menuContents.querySelector(
        '.nav-content > ul'
    ).style.gridAutoColumns = `${maxWidth}px`;
};