widthProperties.js

function smoothScroll(scrollParams) {
  const elementToScroll = scrollParams.element;
  const isWindow = elementToScroll === window;
  const scrollDirectionProp = isWindow ? 'scrollX' : 'scrollLeft';
  const elementWidthProp = isWindow ? 'innerWidth' : 'clientWidth';
  const scrollLengthProp = 'scrollWidth';
  const initialScrollPosition = elementToScroll[scrollDirectionProp];
  ...
}