Javascript，测试是否支持“平滑”的ScrollBy行为

function smoothScrollBy(distance, duration) {
  const start = window.pageYOffset;
  const startTime = 'now' in window.performance ? performance.now() : new Date().getTime();

  function scroll() {
    const currentTime = 'now' in window.performance ? performance.now() : new Date().getTime();
    const timeElapsed = currentTime - startTime;
    const scrollY = easeInOutQuad(timeElapsed, start, distance, duration);
    window.scrollTo(0, scrollY);
    if (timeElapsed < duration) {
      requestAnimationFrame(scroll);
    }
  }

  function easeInOutQuad(t, b, c, d) {
    t /= d / 2;
    if (t < 1) return c / 2 * t * t + b;
    t--;
    return -c / 2 * (t * (t - 2) - 1) + b;
  }

  requestAnimationFrame(scroll);
}

// 使用示例
smoothScrollBy(500, 1000); // 将页面平滑滚动向下500像素，持续时间为1秒