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function setupFixedBg() {
  const $fixed = $('.js-fixed-bg');
  const $wrapper = isSP() ? $(window) : $('.wrapper');
  let _tmpTop = $wrapper.scrollTop();
  (function _update() {
    const top = $wrapper.scrollTop();
    if(top !== _tmpTop) {
      $fixed.css('transform', `translateY(${top}px)`);
    }
    _tmpTop = top;
    requestAnimationFrame(_update);
  })();
  // $wrapper.on('scroll', () => {
  //   const top = $wrapper.scrollTop();
  //   if(top !== _tmpTop) {
  //     $fixed.css('transform', `translateY(${top}px)`);
  //   }
  //   _tmpTop = top;
  // })
}