function updateHeaderHeight() {
        // Get the height of #brx-header
        const headerHeight = document.querySelector('#brx-header').offsetHeight;
          
        // Store the height in the CSS custom property --header-height
        document.documentElement.style.setProperty('--brxw-header-height', headerHeight + 'px');
    }

    // Execute the function as soon as the document is ready
    document.addEventListener('DOMContentLoaded', function() {
        updateHeaderHeight();  // Initial update of header height when the document is ready

        // Update the header height on window resize and orientation change
        window.addEventListener('resize', updateHeaderHeight);
        window.addEventListener('orientationchange', updateHeaderHeight);
});

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Travelling Europe full-time in a DIY campervan conversion. VandogTraveller is a documentation of my vanlife adventures spanning years. Follow along and join in in the comments…