function styleInactiveDropZones(dropZones, getStyles = () => {}, getClasses = () => []) {
    dropZones.forEach(dz => {
        const styles = getStyles(dz);
        Object.keys(styles).forEach(style => {
            dz.style[style] = "";
        });
        getClasses(dz).forEach(c => dz.classList.contains(c) && dz.classList.remove(c));
    });
}
will remove the 'active' styling from given dropzones
@param {Array<HTMLElement>} dropZones
@param {Function} getStyles - maps a dropzone to a styles object
@param {Function} getClasses - maps a dropzone to a classList