js 滚动到 动画

function smoothScrollTo(elementId, duration) {
  var targetElement = document.getElementById(elementId);
  var targetPosition = targetElement.getBoundingClientRect().top;
  var startPosition = window.pageYOffset;
  var distance = targetPosition;
  var startTime = null;

  function animation(currentTime) {
    if (startTime === null) startTime = currentTime;
    var timeElapsed = currentTime - startTime;
    var run = ease(timeElapsed, startPosition, distance, duration);
    window.scrollTo(0, run);
    if (timeElapsed < duration) requestAnimationFrame(animation);
  }

  function ease(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(animation);
}

// 使用方法
document.querySelector('a[href="#section1"]').addEventListener('click', function(event) {
  event.preventDefault();
  smoothScrollTo('section1', 1000); // 滚动到id为section1的元素，动画持续时间为1000毫秒
});